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*
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000006e0  74 69 6f 6e 20 20 20 20  20 20 20 20 20 20 20 20  |tion            |
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00000710  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
*
00000730  2d 2d 2d 2d 2d 2b 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |-----+----------|
00000740  2d 2d 2d 2b 0d 20 20 20  20 20 20 20 7c 20 26 46  |---+.       | &F|
00000750  45 34 46 20 7c 20 44 61  74 61 20 72 65 67 69 73  |E4F | Data regis|
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000007b0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2b  |---------------+|
000007c0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2b 0d 20  |-------------+. |
000007d0  20 20 20 20 20 20 7c 20  26 46 45 34 45 20 7c 20  |      | &FE4E | |
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00000800  20 20 20 20 7c 20 49 45  52 20 20 20 20 20 20 20  |    | IER       |
00000810  20 20 7c 0d 20 20 20 20  20 20 20 2b 2d 2d 2d 2d  |  |.       +----|
00000820  2d 2d 2d 2b 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |---+------------|
00000830  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
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00000850  2d 2d 2d 2d 2d 2d 2d 2b  0d 20 20 20 20 20 20 20  |-------+.       |
00000860  7c 20 26 46 45 34 44 20  7c 20 49 6e 74 65 72 72  || &FE4D | Interr|
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00000890  49 46 52 20 20 20 20 20  20 20 20 20 7c 0d 20 20  |IFR         |.  |
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000008b0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
*
000008d0  2d 2d 2d 2b 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |---+------------|
000008e0  2d 2b 0d 20 20 20 20 20  20 20 7c 20 26 46 45 34  |-+.       | &FE4|
000008f0  43 20 7c 20 50 65 72 69  70 68 65 72 61 6c 20 63  |C | Peripheral c|
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00000940  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00000950  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2b 2d 2d  |-------------+--|
00000960  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2b 0d 20 20 20  |-----------+.   |
00000970  20 20 20 20 7c 20 26 46  45 34 42 20 7c 20 41 75  |    | &FE4B | Au|
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000009a0  20 20 7c 20 41 43 52 20  20 20 20 20 20 20 20 20  |  | ACR         |
000009b0  7c 0d 20 20 20 20 20 20  20 2b 2d 2d 2d 2d 2d 2d  ||.       +------|
000009c0  2d 2b 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |-+--------------|
000009d0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
000009e0  2d 2d 2d 2d 2d 2d 2d 2b  2d 2d 2d 2d 2d 2d 2d 2d  |-------+--------|
000009f0  2d 2d 2d 2d 2d 2b 0d 20  20 20 20 20 20 20 7c 20  |-----+.       | |
00000a00  26 46 45 34 41 20 7c 20  53 68 69 66 74 20 72 65  |&FE4A | Shift re|
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00000a20  20 20 20 20 20 20 20 20  20 20 20 20 7c 20 53 52  |            | SR|
00000a30  20 20 20 20 20 20 20 20  20 20 7c 0d 20 20 20 20  |          |.    |
00000a40  20 20 20 2b 2d 2d 2d 2d  2d 2d 2d 2b 2d 2d 2d 2d  |   +-------+----|
00000a50  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
*
00000a70  2d 2b 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2b  |-+-------------+|
00000a80  0d 20 20 20 20 20 20 20  7c 20 26 46 45 34 39 20  |.       | &FE49 |
00000a90  7c 20 54 69 6d 65 72 20  32 20 69 6e 69 74 69 61  || Timer 2 initia|
00000aa0  74 65 20 63 6f 75 6e 74  20 20 20 20 20 20 20 20  |te count        |
00000ab0  20 20 20 20 20 20 7c 20  54 32 43 48 20 20 20 20  |      | T2CH    |
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00000ad0  2d 2d 2d 2d 2d 2b 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |-----+----------|
00000ae0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00000af0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2b 2d 2d 2d 2d  |-----------+----|
00000b00  2d 2d 2d 2d 2d 2d 2d 2d  2d 2b 0d 20 20 20 20 20  |---------+.     |
00000b10  20 20 7c 20 26 46 45 34  38 20 7c 20 54 69 6d 65  |  | &FE48 | Time|
00000b20  72 20 32 20 77 72 69 74  65 20 6c 61 74 63 68 2c  |r 2 write latch,|
00000b30  20 72 65 61 64 20 63 6f  75 6e 74 65 72 20 20 20  | read counter   |
00000b40  7c 20 54 32 43 4c 20 20  20 20 20 20 20 20 7c 0d  || T2CL        |.|
00000b50  20 20 20 20 20 20 20 2b  2d 2d 2d 2d 2d 2d 2d 2b  |       +-------+|
00000b60  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
*
00000b80  2d 2d 2d 2d 2d 2b 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |-----+----------|
00000b90  2d 2d 2d 2b 0d 20 20 20  20 20 20 20 7c 20 26 46  |---+.       | &F|
00000ba0  45 34 37 20 7c 20 54 69  6d 65 72 20 31 20 6c 6f  |E47 | Timer 1 lo|
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00000bc0  79 74 65 20 20 20 20 20  20 20 7c 20 54 31 4c 48  |yte       | T1LH|
00000bd0  20 20 20 20 20 20 20 20  7c 0d 20 20 20 20 20 20  |        |.      |
00000be0  20 2b 2d 2d 2d 2d 2d 2d  2d 2b 2d 2d 2d 2d 2d 2d  | +-------+------|
00000bf0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00000c00  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2b  |---------------+|
00000c10  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2b 0d 20  |-------------+. |
00000c20  20 20 20 20 20 20 7c 20  26 46 45 34 36 20 7c 20  |      | &FE46 | |
00000c30  54 69 6d 65 72 20 31 20  6c 6f 61 64 20 6c 61 74  |Timer 1 load lat|
00000c40  63 68 2c 20 6c 6f 77 20  62 79 74 65 20 20 20 20  |ch, low byte    |
00000c50  20 20 20 20 7c 20 54 31  4c 4c 20 20 20 20 20 20  |    | T1LL      |
00000c60  20 20 7c 0d 20 20 20 20  20 20 20 2b 2d 2d 2d 2d  |  |.       +----|
00000c70  2d 2d 2d 2b 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |---+------------|
00000c80  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00000c90  2d 2d 2d 2d 2d 2d 2d 2d  2d 2b 2d 2d 2d 2d 2d 2d  |---------+------|
00000ca0  2d 2d 2d 2d 2d 2d 2d 2b  0d 20 20 20 20 20 20 20  |-------+.       |
00000cb0  7c 20 26 46 45 34 35 20  7c 20 54 69 6d 65 72 20  || &FE45 | Timer |
00000cc0  31 20 69 6e 69 74 69 61  74 65 20 63 6f 75 6e 74  |1 initiate count|
00000cd0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 7c 20  |              | |
00000ce0  54 31 43 48 20 20 20 20  20 20 20 20 7c 0d 20 20  |T1CH        |.  |
00000cf0  20 20 20 20 20 2b 2d 2d  2d 2d 2d 2d 2d 2b 2d 2d  |     +-------+--|
00000d00  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
*
00000d20  2d 2d 2d 2b 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |---+------------|
00000d30  2d 2b 0d 20 20 20 20 20  20 20 7c 20 26 46 45 34  |-+.       | &FE4|
00000d40  34 20 7c 20 54 69 6d 65  72 20 31 20 77 72 69 74  |4 | Timer 1 writ|
00000d50  65 20 6c 61 74 63 68 2c  20 72 65 61 64 20 63 6f  |e latch, read co|
00000d60  75 6e 74 65 72 20 20 20  7c 20 54 31 43 4c 20 20  |unter   | T1CL  |
00000d70  20 20 20 20 20 20 7c 0d  20 20 20 20 20 20 20 2b  |      |.       +|
00000d80  2d 2d 2d 2d 2d 2d 2d 2b  2d 2d 2d 2d 2d 2d 2d 2d  |-------+--------|
00000d90  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00000da0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2b 2d 2d  |-------------+--|
00000db0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2b 0d 20 20 20  |-----------+.   |
00000dc0  20 20 20 20 7c 20 26 46  45 34 33 20 7c 20 44 61  |    | &FE43 | Da|
00000dd0  74 61 20 64 69 72 65 63  74 69 6f 6e 20 72 65 67  |ta direction reg|
00000de0  69 73 74 65 72 20 41 20  20 20 20 20 20 20 20 20  |ister A         |
00000df0  20 20 7c 20 44 44 52 41  20 20 20 20 20 20 20 20  |  | DDRA        |
00000e00  7c 0d 20 20 20 20 20 20  20 2b 2d 2d 2d 2d 2d 2d  ||.       +------|
00000e10  2d 2b 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |-+--------------|
00000e20  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00000e30  2d 2d 2d 2d 2d 2d 2d 2b  2d 2d 2d 2d 2d 2d 2d 2d  |-------+--------|
00000e40  2d 2d 2d 2d 2d 2b 0d 20  20 20 20 20 20 20 7c 20  |-----+.       | |
00000e50  26 46 45 34 32 20 7c 20  44 61 74 61 20 64 69 72  |&FE42 | Data dir|
00000e60  65 63 74 69 6f 6e 20 72  65 67 69 73 74 65 72 20  |ection register |
00000e70  42 20 20 20 20 20 20 20  20 20 20 20 7c 20 44 44  |B           | DD|
00000e80  52 42 20 20 20 20 20 20  20 20 7c 0d 20 20 20 20  |RB        |.    |
00000e90  20 20 20 2b 2d 2d 2d 2d  2d 2d 2d 2b 2d 2d 2d 2d  |   +-------+----|
00000ea0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
*
00000ec0  2d 2b 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2b  |-+-------------+|
00000ed0  0d 20 20 20 20 20 20 20  7c 20 26 46 45 34 31 20  |.       | &FE41 |
00000ee0  7c 20 44 61 74 61 20 72  65 67 69 73 74 65 72 20  || Data register |
00000ef0  41 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |A               |
00000f00  20 20 20 20 20 20 7c 20  44 52 41 20 20 20 20 20  |      | DRA     |
00000f10  20 20 20 20 7c 0d 20 20  20 20 20 20 20 2b 2d 2d  |    |.       +--|
00000f20  2d 2d 2d 2d 2d 2b 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |-----+----------|
00000f30  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00000f40  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2b 2d 2d 2d 2d  |-----------+----|
00000f50  2d 2d 2d 2d 2d 2d 2d 2d  2d 2b 0d 20 20 20 20 20  |---------+.     |
00000f60  20 20 7c 20 26 46 45 34  30 20 7c 20 44 61 74 61  |  | &FE40 | Data|
00000f70  20 72 65 67 69 73 74 65  72 20 42 20 20 20 20 20  | register B     |
00000f80  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |                |
00000f90  7c 20 44 52 42 20 20 20  20 20 20 20 20 20 7c 0d  || DRB         |.|
00000fa0  20 20 20 20 20 20 20 2b  2d 2d 2d 2d 2d 2d 2d 2b  |       +-------+|
00000fb0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
*
00000fd0  2d 2d 2d 2d 2d 2b 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |-----+----------|
00000fe0  2d 2d 2d 2b 0d 0d 46 69  67 75 72 65 20 31 20 20  |---+..Figure 1  |
00000ff0  54 68 65 20 53 79 73 74  65 6d 20 56 49 41 20 72  |The System VIA r|
00001000  65 67 69 73 74 65 72 73  0d 2d 2d 2d 2d 2d 2d 2d  |egisters.-------|
00001010  2d 20 20 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |-  -------------|
00001020  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 0d 0d 0d 46 6f  |-----------...Fo|
00001030  75 72 20 6f 66 20 74 68  65 73 65 20 31 36 20 72  |ur of these 16 r|
00001040  65 67 69 73 74 65 72 73  20 61 72 65 20 6f 66 20  |egisters are of |
00001050  69 6e 74 65 72 65 73 74  20 77 68 65 6e 20 75 73  |interest when us|
00001060  69 6e 67 20 61 20 6c 69  67 68 74 20 70 65 6e 2e  |ing a light pen.|
00001070  20 54 68 65 79 0d 61 72  65 20 64 61 74 61 20 72  | They.are data r|
00001080  65 67 69 73 74 65 72 20  42 20 28 26 46 45 34 30  |egister B (&FE40|
00001090  29 2c 20 74 68 65 20 70  65 72 69 70 68 65 72 61  |), the periphera|
000010a0  6c 20 63 6f 6e 74 72 6f  6c 20 72 65 67 69 73 74  |l control regist|
000010b0  65 72 20 28 26 46 45 34  43 29 2c 20 74 68 65 0d  |er (&FE4C), the.|
000010c0  69 6e 74 65 72 72 75 70  74 20 66 6c 61 67 20 72  |interrupt flag r|
000010d0  65 67 69 73 74 65 72 20  28 26 46 45 34 44 29 2c  |egister (&FE4D),|
000010e0  20 61 6e 64 20 74 68 65  20 69 6e 74 65 72 72 75  | and the interru|
000010f0  70 74 20 65 6e 61 62 6c  65 20 72 65 67 69 73 74  |pt enable regist|
00001100  65 72 0d 28 26 46 45 34  45 29 2e 0d 0d 42 6f 74  |er.(&FE4E)...Bot|
00001110  68 20 74 68 65 20 73 79  73 74 65 6d 20 56 49 41  |h the system VIA|
00001120  20 61 6e 64 20 74 68 65  20 75 73 65 72 20 56 49  | and the user VI|
00001130  41 20 68 61 76 65 20 32  30 20 49 2f 4f 20 6c 69  |A have 20 I/O li|
00001140  6e 65 73 20 67 72 6f 75  70 65 64 20 69 6e 74 6f  |nes grouped into|
00001150  20 61 6e 20 41 0d 73 69  64 65 20 61 6e 64 20 61  | an A.side and a|
00001160  20 42 20 73 69 64 65 20  6f 66 20 31 30 20 6c 69  | B side of 10 li|
00001170  6e 65 73 20 65 61 63 68  2e 20 54 68 65 73 65 20  |nes each. These |
00001180  31 30 20 6c 69 6e 65 73  20 61 72 65 20 64 69 76  |10 lines are div|
00001190  69 64 65 64 20 69 6e 74  6f 20 38 20 64 61 74 61  |ided into 8 data|
000011a0  0d 6c 69 6e 65 73 20 61  6e 64 20 32 20 68 61 6e  |.lines and 2 han|
000011b0  64 73 68 61 6b 65 20 6c  69 6e 65 73 2e 20 54 68  |dshake lines. Th|
000011c0  65 20 64 61 74 61 20 6c  69 6e 65 73 20 61 72 65  |e data lines are|
000011d0  20 63 61 6c 6c 65 64 20  50 41 30 20 74 6f 20 50  | called PA0 to P|
000011e0  41 37 20 6f 6e 20 74 68  65 20 41 0d 73 69 64 65  |A7 on the A.side|
000011f0  20 61 6e 64 20 50 42 30  20 74 6f 20 50 42 37 20  | and PB0 to PB7 |
00001200  6f 6e 20 74 68 65 20 42  20 73 69 64 65 2e 20 44  |on the B side. D|
00001210  61 74 61 20 6c 69 6e 65  73 20 50 41 30 20 74 6f  |ata lines PA0 to|
00001220  20 50 41 37 20 63 61 6e  20 62 65 20 72 65 61 64  | PA7 can be read|
00001230  20 66 72 6f 6d 0d 6f 72  20 77 72 69 74 74 65 6e  | from.or written|
00001240  20 74 6f 20 64 61 74 61  20 72 65 67 69 73 74 65  | to data registe|
00001250  72 20 41 20 61 6e 64 20  64 61 74 61 20 6c 69 6e  |r A and data lin|
00001260  65 73 20 50 42 30 20 74  6f 20 50 42 37 20 63 61  |es PB0 to PB7 ca|
00001270  6e 20 62 65 20 72 65 61  64 20 66 72 6f 6d 0d 6f  |n be read from.o|
00001280  72 20 77 72 69 74 74 65  6e 20 74 6f 20 64 61 74  |r written to dat|
00001290  61 20 72 65 67 69 73 74  65 72 20 42 2e 20 44 61  |a register B. Da|
000012a0  74 61 20 72 65 67 69 73  74 65 72 20 42 20 69 73  |ta register B is|
000012b0  20 75 73 65 66 75 6c 20  77 68 65 6e 20 77 72 69  | useful when wri|
000012c0  74 69 6e 67 0d 6c 69 67  68 74 20 70 65 6e 20 73  |ting.light pen s|
000012d0  6f 66 74 77 61 72 65 20  62 65 63 61 75 73 65 20  |oftware because |
000012e0  74 68 65 20 73 74 61 74  75 73 20 6f 66 20 74 68  |the status of th|
000012f0  65 20 74 77 6f 20 66 69  72 65 20 62 75 74 74 6f  |e two fire butto|
00001300  6e 73 20 63 61 6e 20 62  65 20 72 65 61 64 0d 66  |ns can be read.f|
00001310  72 6f 6d 20 74 68 69 73  20 72 65 67 69 73 74 65  |rom this registe|
00001320  72 2e 20 54 68 65 20 72  69 67 68 74 20 66 69 72  |r. The right fir|
00001330  65 20 62 75 74 74 6f 6e  20 63 6c 65 61 72 73 20  |e button clears |
00001340  62 69 74 20 35 20 6f 66  20 44 52 42 20 77 68 65  |bit 5 of DRB whe|
00001350  6e 20 74 68 65 0d 62 75  74 74 6f 6e 20 69 73 20  |n the.button is |
00001360  63 6c 6f 73 65 64 20 61  6e 64 20 73 65 74 73 20  |closed and sets |
00001370  62 69 74 20 66 69 76 65  20 6f 66 20 44 52 42 20  |bit five of DRB |
00001380  77 68 65 6e 20 69 74 20  69 73 20 6f 70 65 6e 2e  |when it is open.|
00001390  20 54 68 65 20 73 74 61  74 75 73 20 6f 66 0d 74  | The status of.t|
000013a0  68 65 20 6c 65 66 74 20  66 69 72 65 20 62 75 74  |he left fire but|
000013b0  74 6f 6e 20 63 61 6e 20  62 65 20 72 65 61 64 20  |ton can be read |
000013c0  66 72 6f 6d 20 62 69 74  20 34 20 6f 66 20 44 52  |from bit 4 of DR|
000013d0  42 2e 0d 0d 54 68 65 20  68 61 6e 64 73 68 61 6b  |B...The handshak|
000013e0  65 20 6c 69 6e 65 73 20  61 72 65 20 63 61 6c 6c  |e lines are call|
000013f0  65 64 20 43 41 31 20 61  6e 64 20 43 41 32 20 6f  |ed CA1 and CA2 o|
00001400  6e 20 74 68 65 20 41 20  73 69 64 65 20 61 6e 64  |n the A side and|
00001410  20 43 42 31 20 61 6e 64  20 43 42 32 0d 6f 6e 20  | CB1 and CB2.on |
00001420  74 68 65 20 42 20 73 69  64 65 2e 20 4c 69 67 68  |the B side. Ligh|
00001430  74 20 70 65 6e 20 69 6e  74 65 72 72 75 70 74 73  |t pen interrupts|
00001440  20 61 72 65 20 72 6f 75  74 65 64 20 74 6f 20 43  | are routed to C|
00001450  42 32 20 6f 66 20 74 68  65 20 73 79 73 74 65 6d  |B2 of the system|
00001460  20 56 49 41 2e 0d 54 68  65 20 70 65 72 69 70 68  | VIA..The periph|
00001470  65 72 61 6c 20 63 6f 6e  74 72 6f 6c 20 72 65 67  |eral control reg|
00001480  69 73 74 65 72 20 69 73  20 75 73 65 64 20 74 6f  |ister is used to|
00001490  20 63 6f 6e 74 72 6f 6c  20 74 68 65 20 75 73 65  | control the use|
000014a0  20 6f 66 20 74 68 65 73  65 0d 68 61 6e 64 73 68  | of these.handsh|
000014b0  61 6b 65 20 6c 69 6e 65  73 2e 20 54 68 65 20 50  |ake lines. The P|
000014c0  43 52 20 61 6e 64 20 74  68 65 20 69 6e 74 65 72  |CR and the inter|
000014d0  70 72 65 74 61 74 69 6f  6e 20 6f 66 20 69 74 73  |pretation of its|
000014e0  20 62 69 74 73 20 69 73  20 73 68 6f 77 6e 20 69  | bits is shown i|
000014f0  6e 0d 66 69 67 75 72 65  20 32 2e 0d 0d 0d 0d 62  |n.figure 2.....b|
00001500  69 74 20 20 20 20 37 20  20 20 20 20 20 20 36 20  |it    7       6 |
00001510  20 20 20 20 20 20 35 20  20 20 20 20 20 20 34 20  |      5       4 |
00001520  20 20 20 20 20 20 33 20  20 20 20 20 20 20 32 20  |      3       2 |
00001530  20 20 20 20 20 20 31 20  20 20 20 20 20 20 30 0d  |      1       0.|
00001540  20 20 20 2b 2d 2d 2d 2d  2d 2d 2d 2b 2d 2d 2d 2d  |   +-------+----|
00001550  2d 2d 2d 2b 2d 2d 2d 2d  2d 2d 2d 2b 2d 2d 2d 2d  |---+-------+----|
*
00001580  2d 2d 2d 2b 0d 20 20 20  7c 20 20 20 20 20 20 20  |---+.   |       |
00001590  20 20 20 43 42 32 20 20  20 20 20 20 20 20 20 20  |   CB2          |
000015a0  7c 20 20 43 42 31 20 20  7c 20 20 20 20 20 20 20  ||  CB1  |       |
000015b0  20 20 20 43 41 32 20 20  20 20 20 20 20 20 20 20  |   CA2          |
000015c0  7c 20 20 43 41 31 20 20  7c 0d 20 20 20 7c 20 20  ||  CA1  |.   |  |
000015d0  20 20 20 20 20 20 63 6f  6e 74 72 6f 6c 20 20 20  |      control   |
000015e0  20 20 20 20 20 7c 63 6f  6e 74 72 6f 6c 7c 20 20  |     |control|  |
000015f0  20 20 20 20 20 20 63 6f  6e 74 72 6f 6c 20 20 20  |      control   |
00001600  20 20 20 20 20 7c 63 6f  6e 74 72 6f 6c 7c 0d 20  |     |control|. |
00001610  20 20 2b 2d 2d 2d 2d 2d  2d 2d 2b 2d 2d 2d 2d 2d  |  +-------+-----|
00001620  2d 2d 2b 2d 2d 2d 2d 2d  2d 2d 2b 2d 2d 2d 2d 2d  |--+-------+-----|
*
00001650  2d 2d 2b 0d 0d 0d 20 42  69 74 20 20 49 6e 74 65  |--+... Bit  Inte|
00001660  72 70 72 65 74 61 74 69  6f 6e 20 69 66 20 62 69  |rpretation if bi|
00001670  74 20 63 6c 65 61 72 20  28 30 29 20 20 20 49 6e  |t clear (0)   In|
00001680  74 65 72 70 72 65 74 61  74 69 6f 6e 20 69 66 20  |terpretation if |
00001690  62 69 74 20 73 65 74 20  28 31 29 0d 2b 2d 2d 2d  |bit set (1).+---|
000016a0  2b 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |+---------------|
000016b0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
000016c0  2d 2d 2b 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |--+-------------|
000016d0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
000016e0  2d 2d 2d 2d 2b 0d 7c 20  30 20 7c 53 65 74 20 62  |----+.| 0 |Set b|
000016f0  69 74 20 31 20 6f 66 20  49 46 52 20 6f 6e 20 2d  |it 1 of IFR on -|
00001700  76 65 20 67 6f 69 6e 67  20 43 41 31 7c 53 65 74  |ve going CA1|Set|
00001710  20 62 69 74 20 31 20 6f  66 20 49 46 52 20 6f 6e  | bit 1 of IFR on|
00001720  20 2b 76 65 20 67 6f 69  6e 67 20 43 41 31 7c 0d  | +ve going CA1|.|
00001730  2b 2d 2d 2d 2b 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |+---+-----------|
00001740  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00001750  2d 2d 2d 2d 2d 2d 2b 2d  2d 2d 2d 2d 2d 2d 2d 2d  |------+---------|
00001760  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00001770  2d 2d 2d 2d 2d 2d 2d 2d  2b 0d 7c 20 31 20 7c 20  |--------+.| 1 | |
00001780  44 52 41 20 73 65 6c 65  63 74 65 64 20 74 6f 20  |DRA selected to |
00001790  63 6c 65 61 72 20 69 6e  74 65 72 72 75 70 74 20  |clear interrupt |
000017a0  7c 20 49 6e 74 65 72 72  75 70 74 20 6e 6f 74 20  || Interrupt not |
000017b0  63 6c 65 61 72 65 64 20  62 79 20 44 52 41 20 20  |cleared by DRA  |
000017c0  20 20 7c 0d 2b 2d 2d 2d  2b 2d 2d 2d 2d 2d 2d 2d  |  |.+---+-------|
000017d0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
000017e0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2b 2d 2d 2d 2d 2d  |----------+-----|
000017f0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00001800  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2b 0d 7c 20  |------------+.| |
00001810  32 20 7c 53 65 74 20 62  69 74 20 30 20 6f 66 20  |2 |Set bit 0 of |
00001820  49 46 52 20 6f 6e 20 2d  76 65 20 67 6f 69 6e 67  |IFR on -ve going|
00001830  20 43 41 32 7c 53 65 74  20 62 69 74 20 30 20 6f  | CA2|Set bit 0 o|
00001840  66 20 49 46 52 20 6f 6e  20 2b 76 65 20 67 6f 69  |f IFR on +ve goi|
00001850  6e 67 20 43 41 32 7c 0d  2b 2d 2d 2d 2b 2d 2d 2d  |ng CA2|.+---+---|
00001860  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00001870  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2b 2d  |--------------+-|
00001880  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
*
000018a0  2b 0d 7c 20 33 20 7c 20  53 65 74 20 43 41 32 20  |+.| 3 | Set CA2 |
000018b0  74 6f 20 69 6e 70 75 74  20 6d 6f 64 65 20 20 20  |to input mode   |
000018c0  20 20 20 20 20 20 20 20  7c 20 53 65 74 20 43 41  |        | Set CA|
000018d0  32 20 74 6f 20 6f 75 74  70 75 74 20 6d 6f 64 65  |2 to output mode|
000018e0  20 20 20 20 20 20 20 20  20 20 7c 0d 2b 2d 2d 2d  |          |.+---|
000018f0  2b 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |+---------------|
00001900  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00001910  2d 2d 2b 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |--+-------------|
00001920  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00001930  2d 2d 2d 2d 2b 0d 7c 20  34 20 7c 53 65 74 20 62  |----+.| 4 |Set b|
00001940  69 74 20 34 20 6f 66 20  49 46 52 20 6f 6e 20 2d  |it 4 of IFR on -|
00001950  76 65 20 67 6f 69 6e 67  20 43 42 31 7c 53 65 74  |ve going CB1|Set|
00001960  20 62 69 74 20 34 20 6f  66 20 49 46 52 20 6f 6e  | bit 4 of IFR on|
00001970  20 2b 76 65 20 67 6f 69  6e 67 20 43 42 31 7c 0d  | +ve going CB1|.|
00001980  2b 2d 2d 2d 2b 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |+---+-----------|
00001990  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
000019a0  2d 2d 2d 2d 2d 2d 2b 2d  2d 2d 2d 2d 2d 2d 2d 2d  |------+---------|
000019b0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
000019c0  2d 2d 2d 2d 2d 2d 2d 2d  2b 0d 7c 20 35 20 7c 20  |--------+.| 5 | |
000019d0  44 52 42 20 73 65 6c 65  63 74 65 64 20 74 6f 20  |DRB selected to |
000019e0  63 6c 65 61 72 20 69 6e  74 65 72 72 75 70 74 20  |clear interrupt |
000019f0  7c 20 49 6e 74 65 72 72  75 70 74 20 6e 6f 74 20  || Interrupt not |
00001a00  63 6c 65 61 72 65 64 20  62 79 20 44 52 42 20 20  |cleared by DRB  |
00001a10  20 20 7c 0d 2b 2d 2d 2d  2b 2d 2d 2d 2d 2d 2d 2d  |  |.+---+-------|
00001a20  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00001a30  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2b 2d 2d 2d 2d 2d  |----------+-----|
00001a40  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00001a50  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2b 0d 7c 20  |------------+.| |
00001a60  36 20 7c 53 65 74 20 62  69 74 20 33 20 6f 66 20  |6 |Set bit 3 of |
00001a70  49 46 52 20 6f 6e 20 2d  76 65 20 67 6f 69 6e 67  |IFR on -ve going|
00001a80  20 43 42 32 7c 53 65 74  20 62 69 74 20 33 20 6f  | CB2|Set bit 3 o|
00001a90  66 20 49 46 52 20 6f 6e  20 2b 76 65 20 67 6f 69  |f IFR on +ve goi|
00001aa0  6e 67 20 43 42 32 7c 0d  2b 2d 2d 2d 2b 2d 2d 2d  |ng CB2|.+---+---|
00001ab0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00001ac0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2b 2d  |--------------+-|
00001ad0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
*
00001af0  2b 0d 7c 20 37 20 7c 20  53 65 74 20 43 42 32 20  |+.| 7 | Set CB2 |
00001b00  74 6f 20 69 6e 70 75 74  20 6d 6f 64 65 20 20 20  |to input mode   |
00001b10  20 20 20 20 20 20 20 20  7c 20 53 65 74 20 43 42  |        | Set CB|
00001b20  32 20 74 6f 20 6f 75 74  70 75 74 20 6d 6f 64 65  |2 to output mode|
00001b30  20 20 20 20 20 20 20 20  20 20 7c 0d 2b 2d 2d 2d  |          |.+---|
00001b40  2b 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |+---------------|
00001b50  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00001b60  2d 2d 2b 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |--+-------------|
00001b70  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00001b80  2d 2d 2d 2d 2b 0d 0d 46  69 67 75 72 65 20 32 20  |----+..Figure 2 |
00001b90  20 54 68 65 20 70 65 72  69 70 68 65 72 61 6c 20  | The peripheral |
00001ba0  63 6f 6e 74 72 6f 6c 20  72 65 67 69 73 74 65 72  |control register|
00001bb0  0d 2d 2d 2d 2d 2d 2d 2d  2d 20 20 2d 2d 2d 2d 2d  |.--------  -----|
00001bc0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00001bd0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 0d 0d 0d 54 68 65  |----------...The|
00001be0  20 6c 69 67 68 74 20 70  65 6e 20 69 6e 74 65 72  | light pen inter|
00001bf0  72 75 70 74 20 69 73 20  72 6f 75 74 65 64 20 74  |rupt is routed t|
00001c00  6f 20 43 42 32 20 61 6e  64 20 73 6f 20 62 69 74  |o CB2 and so bit|
00001c10  73 20 35 2c 20 36 20 61  6e 64 20 37 20 6f 66 20  |s 5, 6 and 7 of |
00001c20  74 68 65 0d 73 79 73 74  65 6d 20 56 49 41 20 50  |the.system VIA P|
00001c30  43 52 20 63 6f 6e 74 72  6f 6c 20 74 68 65 20 69  |CR control the i|
00001c40  6e 74 65 72 70 72 65 74  61 74 69 6f 6e 20 6f 66  |nterpretation of|
00001c50  20 74 68 65 20 76 69 64  65 6f 20 73 74 72 6f 62  | the video strob|
00001c60  65 20 70 75 6c 73 65 2e  20 57 65 0d 77 61 6e 74  |e pulse. We.want|
00001c70  20 75 73 65 20 43 42 32  20 69 6e 20 74 68 65 20  | use CB2 in the |
00001c80  69 6e 70 75 74 20 6d 6f  64 65 20 28 62 69 74 20  |input mode (bit |
00001c90  37 20 63 6c 65 61 72 29  2c 20 74 6f 20 67 65 6e  |7 clear), to gen|
00001ca0  65 72 61 74 65 20 61 6e  20 69 6e 74 65 72 72 75  |erate an interru|
00001cb0  70 74 20 6f 6e 0d 61 20  6e 65 67 61 74 69 76 65  |pt on.a negative|
00001cc0  20 67 6f 69 6e 67 20 70  75 6c 73 65 20 28 62 69  | going pulse (bi|
00001cd0  74 20 36 20 63 6c 65 61  72 29 20 61 6e 64 20 74  |t 6 clear) and t|
00001ce0  6f 20 63 6c 65 61 72 20  74 68 65 20 69 6e 74 65  |o clear the inte|
00001cf0  72 72 75 70 74 20 77 68  65 6e 20 44 52 42 0d 69  |rrupt when DRB.i|
00001d00  73 20 73 65 6c 65 63 74  65 64 20 28 62 69 74 20  |s selected (bit |
00001d10  35 20 63 6c 65 61 72 29  2e 20 54 68 69 73 20 69  |5 clear). This i|
00001d20  73 20 71 75 69 74 65 20  63 6f 6e 76 65 6e 69 65  |s quite convenie|
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00001d40  65 66 61 75 6c 74 2c 0d  62 69 74 73 20 35 2c 20  |efault,.bits 5, |
00001d50  36 20 61 6e 64 20 37 20  6f 66 20 74 68 65 20 73  |6 and 7 of the s|
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00001d80  65 20 62 69 74 73 20 68  61 76 65 20 62 65 65 6e  |e bits have been|
00001d90  0d 63 68 61 6e 67 65 64  20 66 72 6f 6d 20 74 68  |.changed from th|
00001da0  65 69 72 20 64 65 66 61  75 6c 74 20 76 61 6c 75  |eir default valu|
00001db0  65 73 20 79 6f 75 20 64  6f 20 6e 6f 74 20 68 61  |es you do not ha|
00001dc0  76 65 20 74 6f 20 61 6c  74 65 72 20 74 68 65 20  |ve to alter the |
00001dd0  63 6f 6e 74 65 6e 74 73  20 6f 66 0d 74 68 65 20  |contents of.the |
00001de0  50 43 52 20 74 6f 20 75  73 65 20 6c 69 67 68 74  |PCR to use light|
00001df0  20 70 65 6e 20 69 6e 74  65 72 72 75 70 74 73 2e  | pen interrupts.|
00001e00  0d 0d 4c 69 67 68 74 20  70 65 6e 20 69 6e 74 65  |..Light pen inte|
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00001e70  64 64 20 6d 65 74 68 6f  64 2e 20 54 6f 20 61 6c  |dd method. To al|
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00001e90  20 49 45 52 0d 79 6f 75  20 6d 75 73 74 20 77 72  | IER.you must wr|
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00001ec0  20 69 6e 20 74 68 65 20  73 61 6d 65 20 62 69 74  | in the same bit|
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00001ee0  74 20 37 20 6f 66 20 74  68 65 20 6e 75 6d 62 65  |t 7 of the numbe|
00001ef0  72 20 69 73 20 61 20 31  20 74 68 65 6e 20 74 68  |r is a 1 then th|
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00001f20  73 6f 20 62 65 0d 73 65  74 20 74 6f 20 31 2e 20  |so be.set to 1. |
00001f30  49 66 20 62 69 74 20 37  20 6f 66 20 74 68 65 20  |If bit 7 of the |
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00001f60  74 20 28 6f 72 20 62 69  74 73 29 20 77 69 6c 6c  |t (or bits) will|
00001f70  0d 62 65 20 63 6c 65 61  72 65 64 2e 20 54 68 65  |.be cleared. The|
00001f80  20 73 65 6c 65 63 74 65  64 20 62 69 74 73 20 28  | selected bits (|
00001f90  30 20 74 6f 20 36 29 20  61 72 65 20 73 65 74 20  |0 to 6) are set |
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00001fc0  65 74 20 62 69 74 20 33  20 6f 66 20 74 68 65 20  |et bit 3 of the |
00001fd0  49 45 52 20 79 6f 75 20  68 61 76 65 20 74 6f 20  |IER you have to |
00001fe0  77 72 69 74 65 20 74 68  65 20 6e 75 6d 62 65 72  |write the number|
00001ff0  20 26 38 38 20 28 25 31  30 30 30 31 30 30 30 29  | &88 (%10001000)|
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00002080  42 32 20 77 69 6c 6c 20  73 65 74 20 62 69 74 20  |B2 will set bit |
00002090  33 0d 6f 66 20 74 68 65  20 69 6e 74 65 72 72 75  |3.of the interru|
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000020e0  67 6e 69 73 65 64 20 62  65 63 61 75 73 65 20 62  |gnised because b|
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00002130  73 61 62 6c 65 64 20 62  79 20 77 72 69 74 69 6e  |sabled by writin|
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00002150  20 28 25 30 30 30 30 31  30 30 30 29 20 69 6e 74  | (%00001000) int|
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000021d0  46 52 20 62 75 74 20 69  74 20 77 69 6c 6c 20 6e  |FR but it will n|
000021e0  6f 74 20 67 65 6e 65 72  61 74 65 20 61 6e 20 49  |ot generate an I|
000021f0  52 51 0d 69 6e 74 65 72  72 75 70 74 2e 20 4c 69  |RQ.interrupt. Li|
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00002240  31 2c 37 38 2c 31 33 36  20 61 6e 64 20 64 69 73  |1,78,136 and dis|
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00002280  72 75 70 74 20 65 6e 61  62 6c 65 20 61 6e 64 20  |rupt enable and |
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000022c0  66 6c 61 67 20 72 65 67  69 73 74 65 72 20 63 61  |flag register ca|
000022d0  6e 20 62 65 20 69 6e 74  65 72 72 6f 67 61 74 65  |n be interrogate|
000022e0  64 20 62 79 20 61 20 70  72 6f 67 72 61 6d 20 74  |d by a program t|
000022f0  6f 20 73 65 65 20 69 66  20 61 20 6c 69 67 68 74  |o see if a light|
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00002310  63 65 20 6f 66 20 61 6e  20 69 6e 74 65 72 72 75  |ce of an interru|
00002320  70 74 2e 20 54 68 65 20  69 6e 74 65 72 70 72 65  |pt. The interpre|
00002330  74 61 74 69 6f 6e 20 6f  66 20 74 68 65 20 62 69  |tation of the bi|
00002340  74 73 20 69 6e 20 74 68  65 20 73 79 73 74 65 6d  |ts in the system|
00002350  0d 56 49 41 20 69 6e 74  65 72 72 75 70 74 20 66  |.VIA interrupt f|
00002360  6c 61 67 20 72 65 67 69  73 74 65 72 20 69 73 20  |lag register is |
00002370  74 61 62 75 6c 61 74 65  64 20 69 6e 20 66 69 67  |tabulated in fig|
00002380  75 72 65 20 33 20 77 68  69 63 68 20 73 68 6f 77  |ure 3 which show|
00002390  73 20 74 68 61 74 20 62  69 74 73 0d 37 20 61 6e  |s that bits.7 an|
000023a0  64 20 33 20 6f 66 20 74  68 65 20 49 46 52 20 77  |d 3 of the IFR w|
000023b0  69 6c 6c 20 62 65 20 73  65 74 20 69 66 20 61 20  |ill be set if a |
000023c0  6c 69 67 68 74 20 70 65  6e 20 69 73 20 74 68 65  |light pen is the|
000023d0  20 73 6f 75 72 63 65 20  6f 66 20 61 6e 0d 69 6e  | source of an.in|
000023e0  74 65 72 72 75 70 74 2e  20 49 66 20 65 69 74 68  |terrupt. If eith|
000023f0  65 72 20 62 69 74 20 37  20 6f 72 20 62 69 74 20  |er bit 7 or bit |
00002400  33 20 6f 66 20 74 68 65  20 49 46 52 20 69 73 20  |3 of the IFR is |
00002410  63 6c 65 61 72 20 74 68  65 6e 20 61 20 6c 69 67  |clear then a lig|
00002420  68 74 20 70 65 6e 0d 77  61 73 20 6e 6f 74 20 74  |ht pen.was not t|
00002430  68 65 20 73 6f 75 72 63  65 20 6f 66 20 61 6e 20  |he source of an |
00002440  69 6e 74 65 72 72 75 70  74 2e 0d 0d 0d 0d 20 20  |interrupt.....  |
00002450  20 20 20 20 20 20 20 20  20 20 20 37 20 20 20 20  |           7    |
00002460  20 20 20 36 20 20 20 20  20 35 20 20 20 20 20 34  |   6     5     4|
00002470  20 20 20 20 20 33 20 20  20 20 20 32 20 20 20 20  |     3     2    |
00002480  20 31 20 20 20 20 20 30  0d 20 20 20 20 20 20 20  | 1     0.       |
00002490  20 2b 2d 2d 2d 2d 2d 2d  2d 2d 2d 2b 2d 2d 2d 2d  | +---------+----|
000024a0  2d 2b 2d 2d 2d 2d 2d 2b  2d 2d 2d 2d 2d 2b 2d 2d  |-+-----+-----+--|
000024b0  2d 2d 2d 2b 2d 2d 2d 2d  2d 2b 2d 2d 2d 2d 2d 2b  |---+-----+-----+|
000024c0  2d 2d 2d 2d 2d 2b 0d 20  20 26 46 45 34 45 20 7c  |-----+.  &FE4E ||
000024d0  53 65 74 2f 43 6c 65 61  72 7c 20 54 31 20 20 7c  |Set/Clear| T1  ||
000024e0  20 54 32 20 20 7c 20 43  42 31 20 7c 20 43 42 32  | T2  | CB1 | CB2|
000024f0  20 7c 20 53 52 20 20 7c  20 43 41 31 20 7c 20 43  | | SR  | CA1 | C|
00002500  41 32 20 7c 20 49 45 52  0d 20 20 20 20 20 20 20  |A2 | IER.       |
00002510  20 2b 2d 2d 2d 2d 2d 2d  2d 2d 2d 2b 2d 2d 2d 2d  | +---------+----|
00002520  2d 2b 2d 2d 2d 2d 2d 2b  2d 2d 2d 2d 2d 2b 2d 2d  |-+-----+-----+--|
00002530  2d 2d 2d 2b 2d 2d 2d 2d  2d 2b 2d 2d 2d 2d 2d 2b  |---+-----+-----+|
00002540  2d 2d 2d 2d 2d 2b 0d 20  20 26 46 45 34 44 20 7c  |-----+.  &FE4D ||
00002550  20 20 20 49 52 51 20 20  20 7c 20 54 31 20 20 7c  |   IRQ   | T1  ||
00002560  20 54 32 20 20 7c 20 43  42 31 20 7c 20 43 42 32  | T2  | CB1 | CB2|
00002570  20 7c 20 53 52 20 20 7c  20 43 41 31 20 7c 20 43  | | SR  | CA1 | C|
00002580  41 32 20 7c 20 49 46 52  0d 20 20 20 20 20 20 20  |A2 | IFR.       |
00002590  20 2b 2d 2d 2d 2d 2d 2d  2d 2d 2d 2b 2d 2d 2d 2d  | +---------+----|
000025a0  2d 2b 2d 2d 2d 2d 2d 2b  2d 2d 2d 2d 2d 2b 2d 2d  |-+-----+-----+--|
000025b0  2d 2d 2d 2b 2d 2d 2d 2d  2d 2b 2d 2d 2d 2d 2d 2b  |---+-----+-----+|
000025c0  2d 2d 2d 2d 2d 2b 0d 0d  0d 0d 20 42 69 74 20 20  |-----+.... Bit  |
000025d0  20 43 61 75 73 65 20 6f  66 20 69 6e 74 65 72 72  | Cause of interr|
000025e0  75 70 74 20 20 20 20 20  20 20 20 49 6e 74 65 72  |upt        Inter|
000025f0  70 72 65 74 61 74 69 6f  6e 0d 2b 2d 2d 2d 2b 2d  |pretation.+---+-|
00002600  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00002610  2d 2d 2d 2d 2d 2d 2d 2d  2b 2d 2d 2d 2d 2d 2d 2d  |--------+-------|
00002620  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
*
00002640  2d 2d 2b 0d 7c 20 30 20  7c 20 43 68 61 6e 67 65  |--+.| 0 | Change|
00002650  20 6f 66 20 73 69 67 6e  61 6c 20 6f 6e 20 43 41  | of signal on CA|
00002660  32 20 7c 20 4b 65 79 20  70 72 65 73 73 65 64 20  |2 | Key pressed |
00002670  6f 6e 20 6b 65 79 62 6f  61 72 64 20 20 20 20 20  |on keyboard     |
00002680  20 20 20 20 20 20 20 20  20 20 20 20 7c 0d 2b 2d  |            |.+-|
00002690  2d 2d 2b 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |--+-------------|
000026a0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2b 2d 2d 2d  |------------+---|
000026b0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
*
000026d0  2d 2d 2d 2d 2d 2d 2b 0d  7c 20 31 20 7c 20 43 68  |------+.| 1 | Ch|
000026e0  61 6e 67 65 20 6f 66 20  73 69 67 6e 61 6c 20 6f  |ange of signal o|
000026f0  6e 20 43 41 31 20 7c 20  56 65 72 74 69 63 61 6c  |n CA1 | Vertical|
00002700  20 73 79 6e 63 20 70 75  6c 73 65 20 20 20 20 20  | sync pulse     |
00002710  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |                |
00002720  7c 0d 2b 2d 2d 2d 2b 2d  2d 2d 2d 2d 2d 2d 2d 2d  ||.+---+---------|
00002730  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00002740  2b 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |+---------------|
00002750  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00002760  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2b 0d 7c 20 32 20  |----------+.| 2 |
00002770  7c 20 43 6f 6d 70 6c 65  74 69 6f 6e 20 6f 66 20  || Completion of |
00002780  38 20 73 68 69 66 74 73  20 20 7c 20 53 68 69 66  |8 shifts  | Shif|
00002790  74 20 72 65 67 69 73 74  65 72 20 69 73 20 6e 6f  |t register is no|
000027a0  74 20 75 73 65 64 20 62  79 20 73 79 73 74 65 6d  |t used by system|
000027b0  2e 20 20 20 7c 0d 7c 20  20 20 7c 20 69 6e 20 74  |.   |.|   | in t|
000027c0  68 65 20 73 68 69 66 74  20 72 65 67 69 73 74 65  |he shift registe|
000027d0  72 20 20 20 7c 20 41 6c  77 61 79 73 20 70 61 73  |r   | Always pas|
000027e0  73 65 64 20 74 6f 20 49  52 51 32 56 20 20 20 20  |sed to IRQ2V    |
000027f0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 7c 0d  |              |.|
00002800  2b 2d 2d 2d 2b 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |+---+-----------|
00002810  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2b 2d  |--------------+-|
00002820  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
*
00002840  2d 2d 2d 2d 2d 2d 2d 2d  2b 0d 7c 20 33 20 7c 20  |--------+.| 3 | |
00002850  43 68 61 6e 67 65 20 6f  66 20 73 69 67 6e 61 6c  |Change of signal|
00002860  20 6f 6e 20 43 42 32 20  7c 20 4c 69 67 68 74 20  | on CB2 | Light |
00002870  70 65 6e 20 69 6e 74 65  72 72 75 70 74 2e 20 4e  |pen interrupt. N|
00002880  6f 74 20 75 73 65 64 20  62 79 20 73 79 73 74 65  |ot used by syste|
00002890  6d 20 7c 0d 7c 20 20 20  7c 20 20 20 20 20 20 20  |m |.|   |       |
000028a0  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |                |
000028b0  20 20 7c 20 41 6c 77 61  79 73 20 70 61 73 73 65  |  | Always passe|
000028c0  64 20 74 6f 20 75 73 65  72 20 72 6f 75 74 69 6e  |d to user routin|
000028d0  65 20 76 69 61 20 49 52  51 32 56 20 7c 0d 2b 2d  |e via IRQ2V |.+-|
000028e0  2d 2d 2b 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |--+-------------|
000028f0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2b 2d 2d 2d  |------------+---|
00002900  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
*
00002920  2d 2d 2d 2d 2d 2d 2b 0d  7c 20 34 20 7c 20 43 68  |------+.| 4 | Ch|
00002930  61 6e 67 65 20 6f 66 20  73 69 67 6e 61 6c 20 6f  |ange of signal o|
00002940  6e 20 43 42 31 20 7c 20  41 44 43 20 63 6f 6e 76  |n CB1 | ADC conv|
00002950  65 72 73 69 6f 6e 20 63  6f 6d 70 6c 65 74 65 64  |ersion completed|
00002960  20 20 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |                |
00002970  7c 0d 2b 2d 2d 2d 2b 2d  2d 2d 2d 2d 2d 2d 2d 2d  ||.+---+---------|
00002980  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00002990  2b 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |+---------------|
000029a0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
000029b0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2b 0d 7c 20 35 20  |----------+.| 5 |
000029c0  7c 20 54 69 6d 65 72 20  32 20 63 6f 6d 70 6c 65  || Timer 2 comple|
000029d0  74 65 20 20 20 20 20 20  20 20 7c 20 43 75 72 72  |te        | Curr|
000029e0  65 6e 74 20 73 70 65 65  63 68 20 77 6f 72 64 20  |ent speech word |
000029f0  63 6f 6d 70 6c 65 74 65  20 20 20 20 20 20 20 20  |complete        |
00002a00  20 20 20 20 7c 0d 2b 2d  2d 2d 2b 2d 2d 2d 2d 2d  |    |.+---+-----|
00002a10  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00002a20  2d 2d 2d 2d 2b 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----+-----------|
00002a30  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00002a40  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2b 0d  |--------------+.|
00002a50  7c 20 36 20 7c 20 54 69  6d 65 72 20 31 20 63 6f  || 6 | Timer 1 co|
00002a60  6d 70 6c 65 74 65 20 20  20 20 20 20 20 20 7c 20  |mplete        | |
00002a70  49 6e 63 72 65 6d 65 6e  74 20 69 6e 74 65 72 6e  |Increment intern|
00002a80  61 6c 20 63 6c 6f 63 6b  20 20 20 20 20 20 20 20  |al clock        |
00002a90  20 20 20 20 20 20 20 20  7c 0d 2b 2d 2d 2d 2b 2d  |        |.+---+-|
00002aa0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
00002ab0  2d 2d 2d 2d 2d 2d 2d 2d  2b 2d 2d 2d 2d 2d 2d 2d  |--------+-------|
00002ac0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
*
00002ae0  2d 2d 2b 0d 7c 20 37 20  7c 20 41 6e 79 20 62 69  |--+.| 7 | Any bi|
00002af0  74 2c 20 30 20 74 6f 20  36 2c 20 69 73 20 73 65  |t, 0 to 6, is se|
00002b00  74 20 7c 20 4f 6e 65 20  6f 66 20 74 68 65 20 61  |t | One of the a|
00002b10  62 6f 76 65 20 69 6e 74  65 72 72 75 70 74 73 20  |bove interrupts |
00002b20  68 61 73 20 6f 63 63 75  72 65 64 20 7c 0d 2b 2d  |has occured |.+-|
00002b30  2d 2d 2b 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |--+-------------|
00002b40  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2b 2d 2d 2d  |------------+---|
00002b50  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
*
00002b70  2d 2d 2d 2d 2d 2d 2b 0d  0d 46 69 67 75 72 65 20  |------+..Figure |
00002b80  33 2e 20 54 68 65 20 69  6e 74 65 72 70 72 65 74  |3. The interpret|
00002b90  61 74 69 6f 6e 20 6f 66  20 74 68 65 20 73 79 73  |ation of the sys|
00002ba0  74 65 6d 20 69 6e 74 65  72 72 75 70 74 20 66 6c  |tem interrupt fl|
00002bb0  61 67 20 72 65 67 69 73  74 65 72 0d 2d 2d 2d 2d  |ag register.----|
00002bc0  2d 2d 2d 2d 2d 20 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----- ----------|
00002bd0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 2d 2d  |----------------|
*
00002bf0  2d 2d 2d 2d 2d 2d 2d 2d  2d 2d 2d 2d 2d 2d 0d 0d  |--------------..|
00002c00  0d 41 20 70 72 6f 67 72  61 6d 20 73 68 6f 75 6c  |.A program shoul|
00002c10  64 20 69 6e 74 65 72 6f  67 61 74 65 20 62 69 74  |d interogate bit|
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00002c50  68 74 20 70 65 6e 20 69  73 20 74 68 65 20 73 6f  |ht pen is the so|
00002c60  75 72 63 65 20 6f 66 20  61 6e 20 49 52 51 20 69  |urce of an IRQ i|
00002c70  6e 74 65 72 72 75 70 74  2e 20 49 66 20 69 74 20  |nterrupt. If it |
00002c80  69 73 20 74 68 65 6e 20  74 68 65 20 69 6e 74 65  |is then the inte|
00002c90  72 72 75 70 74 0d 6d 75  73 74 20 62 65 20 63 6c  |rrupt.must be cl|
00002ca0  65 61 72 65 64 20 62 79  20 72 65 61 64 69 6e 67  |eared by reading|
00002cb0  20 74 68 65 20 63 6f 6e  74 65 6e 74 73 20 6f 66  | the contents of|
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00002cf0  6e 20 74 68 65 72 65 66  6f 72 65 20 72 65 61 64  |n therefore read|
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00002d30  74 65 72 72 75 70 74 20  61 74 20 74 68 65 20 73  |terrupt at the s|
00002d40  61 6d 65 20 74 69 6d 65  2e 0d 0d 54 68 65 20 70  |ame time...The p|
00002d50  72 6f 67 72 61 6d 20 49  4f 49 4e 54 45 52 20 75  |rogram IOINTER u|
00002d60  73 65 73 20 74 68 69 73  20 6d 65 74 68 6f 64 20  |ses this method |
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00002d80  74 61 74 75 73 20 6f 66  20 74 68 65 20 72 69 67  |tatus of the rig|
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00002db0  6e 20 26 37 32 20 66 6f  72 20 74 68 65 20 70 72  |n &72 for the pr|
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00002e60  73 65 64 20 62 75 74 20  69 74 20 64 6f 65 73 0d  |sed but it does.|
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00002f70  6c 61 73 74 20 69 6e 74  65 72 72 75 70 74 2e 20  |last interrupt. |
00002f80  49 6e 20 61 6c 6c 20 74  68 65 0d 64 65 6d 6f 6e  |In all the.demon|
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000031f0  53 45 20 3d 46 41 4c 53  45 0d 0d 54 68 65 72 65  |SE =FALSE..There|
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000034f0  20 49 4f 49 4e 54 45 52  2e 20 49 66 20 79 6f 75  | IOINTER. If you|
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00003580  20 6f 66 20 6c 69 67 68  74 20 70 65 6e 20 69 6e  | of light pen in|
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000035b0  45 52 2e 0d 54 68 65 20  66 69 72 73 74 20 74 69  |ER..The first ti|
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00003660  6d 6d 65 64 20 77 69 74  68 20 74 68 65 20 6c 65  |mmed with the le|
00003670  66 74 20 61 6e 64 20 72  69 67 68 74 20 63 75 72  |ft and right cur|
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00003690  63 6b 67 72 6f 75 6e 64  20 63 6f 6c 6f 75 72 20  |ckground colour |
000036a0  63 61 6e 20 62 65 20 61  6c 74 65 72 65 64 20 62  |can be altered b|
000036b0  79 20 70 72 65 73 73 69  6e 67 20 50 20 28 50 20  |y pressing P (P |
000036c0  66 6f 72 20 70 61 70 65  72 29 20 61 6e 64 20 74  |for paper) and t|
000036d0  68 65 0d 74 65 78 74 20  63 6f 6c 6f 75 72 20 63  |he.text colour c|
000036e0  61 6e 20 62 65 20 61 6c  74 65 72 65 64 20 77 69  |an be altered wi|
000036f0  74 68 20 49 20 28 49 20  66 6f 72 20 69 6e 6b 29  |th I (I for ink)|
00003700  2e 20 54 68 65 20 70 72  6f 67 72 61 6d 20 77 69  |. The program wi|
00003710  6c 6c 20 64 72 61 77 20  61 6e 0d 61 73 74 65 72  |ll draw an.aster|
00003720  69 73 6b 20 6f 6e 20 74  68 65 20 73 63 72 65 65  |isk on the scree|
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00003740  69 67 68 74 20 70 65 6e  20 73 77 69 74 63 68 20  |ight pen switch |
00003750  69 73 20 6f 70 65 6e 2c  20 69 65 2e 20 70 72 65  |is open, ie. pre|
00003760  73 73 65 64 2e 0d 59 6f  75 20 63 61 6e 20 6c 65  |ssed..You can le|
00003770  61 76 65 20 74 68 65 20  70 72 6f 67 72 61 6d 20  |ave the program |
00003780  62 79 20 70 72 65 73 73  69 6e 67 20 74 68 65 20  |by pressing the |
00003790  45 73 63 61 70 65 20 6b  65 79 2e 20 54 68 69 73  |Escape key. This|
000037a0  20 77 69 6c 6c 20 63 61  6c 6c 20 74 68 65 0d 6d  | will call the.m|
000037b0  61 63 68 69 6e 65 20 63  6f 64 65 20 61 20 73 65  |achine code a se|
000037c0  63 6f 6e 64 20 74 69 6d  65 20 61 6e 64 20 64 69  |cond time and di|
000037d0  73 61 62 6c 65 20 74 68  65 20 69 6e 74 65 72 72  |sable the interr|
000037e0  75 70 74 20 72 6f 75 74  69 6e 65 2e 0d 0d 0d 20  |upt routine.... |
000037f0  20 20 31 30 20 52 45 4d  3e 20 49 4f 49 4e 54 45  |  10 REM> IOINTE|
00003800  52 0d 20 20 20 32 30 20  41 25 3d 26 45 41 0d 20  |R.   20 A%=&EA. |
00003810  20 20 33 30 20 58 25 3d  30 0d 20 20 20 34 30 20  |  30 X%=0.   40 |
00003820  59 25 3d 26 46 46 0d 20  20 20 35 30 20 49 46 20  |Y%=&FF.   50 IF |
00003830  28 28 55 53 52 28 26 46  46 46 34 29 41 4e 44 26  |((USR(&FFF4)AND&|
00003840  46 46 30 30 29 44 49 56  26 31 30 30 29 3c 3e 30  |FF00)DIV&100)<>0|
00003850  20 45 4e 44 0d 20 20 20  36 30 20 6d 63 6f 64 65  | END.   60 mcode|
00003860  3d 26 41 30 30 0d 20 20  20 37 30 20 78 63 6f 6f  |=&A00.   70 xcoo|
00003870  72 64 3d 26 37 30 0d 20  20 20 38 30 20 79 63 6f  |rd=&70.   80 yco|
00003880  6f 72 64 3d 26 37 31 0d  20 20 20 39 30 20 21 78  |ord=&71.   90 !x|
00003890  63 6f 6f 72 64 3d 30 0d  20 20 31 30 30 20 50 52  |coord=0.  100 PR|
000038a0  4f 43 6d 63 6f 64 65 0d  20 20 31 31 30 20 4f 4e  |OCmcode.  110 ON|
000038b0  45 52 52 4f 52 20 43 41  4c 4c 20 6d 63 6f 64 65  |ERROR CALL mcode|
000038c0  3a 56 44 55 32 33 2c 31  2c 31 3b 30 3b 30 3b 30  |:VDU23,1,1;0;0;0|
000038d0  3b 3a 45 4e 44 0d 20 20  31 32 30 20 6d 6f 64 65  |;:END.  120 mode|
000038e0  3d 34 0d 20 20 31 33 30  20 70 61 70 65 72 3d 36  |=4.  130 paper=6|
000038f0  0d 20 20 31 34 30 20 69  6e 6b 3d 34 0d 20 20 31  |.  140 ink=4.  1|
00003900  35 30 20 4d 4f 44 45 20  6d 6f 64 65 0d 20 20 31  |50 MODE mode.  1|
00003910  36 30 20 50 52 4f 43 6e  65 77 6d 6f 64 65 0d 20  |60 PROCnewmode. |
00003920  20 31 37 30 20 52 45 50  45 41 54 0d 20 20 31 38  | 170 REPEAT.  18|
00003930  30 20 49 46 20 49 4e 4b  45 59 28 2d 35 38 29 20  |0 IF INKEY(-58) |
00003940  50 52 4f 43 75 70 3a 4d  4f 44 45 20 6d 6f 64 65  |PROCup:MODE mode|
00003950  3a 50 52 4f 43 6e 65 77  6d 6f 64 65 0d 20 20 31  |:PROCnewmode.  1|
00003960  39 30 20 49 46 20 49 4e  4b 45 59 28 2d 34 32 29  |90 IF INKEY(-42)|
00003970  20 50 52 4f 43 64 6f 77  6e 3a 4d 4f 44 45 20 6d  | PROCdown:MODE m|
00003980  6f 64 65 3a 50 52 4f 43  6e 65 77 6d 6f 64 65 0d  |ode:PROCnewmode.|
00003990  20 20 32 30 30 20 49 46  20 49 4e 4b 45 59 28 2d  |  200 IF INKEY(-|
000039a0  35 36 29 20 50 52 4f 43  70 61 70 65 72 0d 20 20  |56) PROCpaper.  |
000039b0  32 31 30 20 49 46 20 49  4e 4b 45 59 28 2d 33 38  |210 IF INKEY(-38|
000039c0  29 20 50 52 4f 43 69 6e  6b 0d 20 20 32 32 30 20  |) PROCink.  220 |
000039d0  49 46 20 49 4e 4b 45 59  28 2d 32 36 29 20 50 52  |IF INKEY(-26) PR|
000039e0  4f 43 6c 65 66 74 0d 20  20 32 33 30 20 49 46 20  |OCleft.  230 IF |
000039f0  49 4e 4b 45 59 28 2d 31  32 32 29 20 50 52 4f 43  |INKEY(-122) PROC|
00003a00  72 69 67 68 74 0d 20 20  32 34 30 20 50 52 49 4e  |right.  240 PRIN|
00003a10  54 54 41 42 28 31 33 2c  32 29 3b 3f 78 63 6f 6f  |TTAB(13,2);?xcoo|
00003a20  72 64 3b 22 20 22 54 41  42 28 31 33 2c 33 29 3b  |rd;" "TAB(13,3);|
00003a30  3f 79 63 6f 6f 72 64 3b  22 20 22 0d 20 20 32 35  |?ycoord;" ".  25|
00003a40  30 20 49 46 20 46 4e 73  77 69 74 63 68 20 56 44  |0 IF FNswitch VD|
00003a50  55 33 31 2c 3f 78 63 6f  6f 72 64 2c 3f 79 63 6f  |U31,?xcoord,?yco|
00003a60  6f 72 64 2c 34 32 0d 20  20 32 36 30 20 55 4e 54  |ord,42.  260 UNT|
00003a70  49 4c 20 46 41 4c 53 45  0d 20 20 32 37 30 20 3a  |IL FALSE.  270 :|
00003a80  0d 20 20 32 38 30 20 44  45 46 50 52 4f 43 75 70  |.  280 DEFPROCup|
00003a90  0d 20 20 32 39 30 20 6d  6f 64 65 3d 6d 6f 64 65  |.  290 mode=mode|
00003aa0  2b 31 0d 20 20 33 30 30  20 49 46 20 6d 6f 64 65  |+1.  300 IF mode|
00003ab0  3e 37 20 6d 6f 64 65 3d  37 0d 20 20 33 31 30 20  |>7 mode=7.  310 |
00003ac0  45 4e 44 50 52 4f 43 0d  20 20 33 32 30 20 3a 0d  |ENDPROC.  320 :.|
00003ad0  20 20 33 33 30 20 44 45  46 50 52 4f 43 64 6f 77  |  330 DEFPROCdow|
00003ae0  6e 0d 20 20 33 34 30 20  6d 6f 64 65 3d 6d 6f 64  |n.  340 mode=mod|
00003af0  65 2d 31 0d 20 20 33 35  30 20 49 46 20 6d 6f 64  |e-1.  350 IF mod|
00003b00  65 3c 30 20 6d 6f 64 65  3d 30 0d 20 20 33 36 30  |e<0 mode=0.  360|
00003b10  20 45 4e 44 50 52 4f 43  0d 20 20 33 37 30 20 3a  | ENDPROC.  370 :|
00003b20  0d 20 20 33 38 30 20 44  45 46 50 52 4f 43 6c 65  |.  380 DEFPROCle|
00003b30  66 74 0d 20 20 33 39 30  20 49 46 20 6f 66 66 73  |ft.  390 IF offs|
00003b40  65 74 6c 6f 77 3f 6d 6f  64 65 3d 31 32 20 45 4e  |etlow?mode=12 EN|
00003b50  44 50 52 4f 43 0d 20 20  34 30 30 20 6f 66 66 73  |DPROC.  400 offs|
00003b60  65 74 6c 6f 77 3f 6d 6f  64 65 3d 6f 66 66 73 65  |etlow?mode=offse|
00003b70  74 6c 6f 77 3f 6d 6f 64  65 2b 31 0d 20 20 34 31  |tlow?mode+1.  41|
00003b80  30 20 50 52 4f 43 64 65  6c 61 79 0d 20 20 34 32  |0 PROCdelay.  42|
00003b90  30 20 45 4e 44 50 52 4f  43 0d 20 20 34 33 30 20  |0 ENDPROC.  430 |
00003ba0  3a 0d 20 20 34 34 30 20  44 45 46 50 52 4f 43 72  |:.  440 DEFPROCr|
00003bb0  69 67 68 74 0d 20 20 34  35 30 20 49 46 20 6f 66  |ight.  450 IF of|
00003bc0  66 73 65 74 6c 6f 77 3f  6d 6f 64 65 3d 30 20 45  |fsetlow?mode=0 E|
00003bd0  4e 44 50 52 4f 43 0d 20  20 34 36 30 20 6f 66 66  |NDPROC.  460 off|
00003be0  73 65 74 6c 6f 77 3f 6d  6f 64 65 3d 6f 66 66 73  |setlow?mode=offs|
00003bf0  65 74 6c 6f 77 3f 6d 6f  64 65 2d 31 0d 20 20 34  |etlow?mode-1.  4|
00003c00  37 30 20 50 52 4f 43 64  65 6c 61 79 0d 20 20 34  |70 PROCdelay.  4|
00003c10  38 30 20 45 4e 44 50 52  4f 43 0d 20 20 34 39 30  |80 ENDPROC.  490|
00003c20  20 3a 0d 20 20 35 30 30  20 44 45 46 50 52 4f 43  | :.  500 DEFPROC|
00003c30  6e 65 77 6d 6f 64 65 0d  20 20 35 31 30 20 56 44  |newmode.  510 VD|
00003c40  55 32 33 2c 31 2c 30 3b  30 3b 30 3b 30 3b 0d 20  |U23,1,0;0;0;0;. |
00003c50  20 35 32 30 20 49 46 20  6d 6f 64 65 3d 37 20 50  | 520 IF mode=7 P|
00003c60  52 4f 43 73 65 76 65 6e  3a 45 4e 44 50 52 4f 43  |ROCseven:ENDPROC|
00003c70  0d 20 20 35 33 30 20 56  44 55 31 39 2c 30 2c 70  |.  530 VDU19,0,p|
00003c80  61 70 65 72 3b 30 3b 0d  20 20 35 34 30 20 56 44  |aper;0;.  540 VD|
00003c90  55 31 39 2c 31 2c 69 6e  6b 3b 30 3b 0d 20 20 35  |U19,1,ink;0;.  5|
00003ca0  35 30 20 43 4f 4c 4f 55  52 31 0d 20 20 35 36 30  |50 COLOUR1.  560|
00003cb0  20 50 52 4f 43 64 65 6c  61 79 0d 20 20 35 37 30  | PROCdelay.  570|
00003cc0  20 45 4e 44 50 52 4f 43  0d 20 20 35 38 30 20 3a  | ENDPROC.  580 :|
00003cd0  0d 20 20 35 39 30 20 44  45 46 50 52 4f 43 64 65  |.  590 DEFPROCde|
00003ce0  6c 61 79 0d 20 20 36 30  30 20 50 52 49 4e 54 54  |lay.  600 PRINTT|
00003cf0  41 42 28 33 2c 31 29 22  4d 6f 64 65 20 22 3b 6d  |AB(3,1)"Mode ";m|
00003d00  6f 64 65 0d 20 20 36 31  30 20 50 52 49 4e 54 54  |ode.  610 PRINTT|
00003d10  41 42 28 33 2c 32 29 22  58 20 63 6f 6f 72 64 20  |AB(3,2)"X coord |
00003d20  3d 20 22 3b 3f 78 63 6f  6f 72 64 0d 20 20 36 32  |= ";?xcoord.  62|
00003d30  30 20 50 52 49 4e 54 54  41 42 28 33 2c 33 29 22  |0 PRINTTAB(3,3)"|
00003d40  59 20 63 6f 6f 72 64 20  3d 20 22 3b 3f 79 63 6f  |Y coord = ";?yco|
00003d50  6f 72 64 0d 20 20 36 33  30 20 50 52 49 4e 54 54  |ord.  630 PRINTT|
00003d60  41 42 28 33 2c 34 29 22  6f 66 66 73 65 74 6c 6f  |AB(3,4)"offsetlo|
00003d70  77 20 3d 20 22 3b 6f 66  66 73 65 74 6c 6f 77 3f  |w = ";offsetlow?|
00003d80  6d 6f 64 65 0d 20 20 36  34 30 20 74 69 6d 65 3d  |mode.  640 time=|
00003d90  54 49 4d 45 2b 32 30 0d  20 20 36 35 30 20 52 45  |TIME+20.  650 RE|
00003da0  50 45 41 54 20 55 4e 54  49 4c 20 74 69 6d 65 3c  |PEAT UNTIL time<|
00003db0  54 49 4d 45 0d 20 20 36  36 30 20 45 4e 44 50 52  |TIME.  660 ENDPR|
00003dc0  4f 43 0d 20 20 36 37 30  20 3a 0d 20 20 36 38 30  |OC.  670 :.  680|
00003dd0  20 44 45 46 50 52 4f 43  69 6e 6b 0d 20 20 36 39  | DEFPROCink.  69|
00003de0  30 20 69 6e 6b 3d 69 6e  6b 2b 31 0d 20 20 37 30  |0 ink=ink+1.  70|
00003df0  30 20 49 46 20 69 6e 6b  3d 70 61 70 65 72 20 69  |0 IF ink=paper i|
00003e00  6e 6b 3d 69 6e 6b 2b 31  0d 20 20 37 31 30 20 49  |nk=ink+1.  710 I|
00003e10  46 20 69 6e 6b 3e 37 20  69 6e 6b 3d 30 0d 20 20  |F ink>7 ink=0.  |
00003e20  37 32 30 20 56 44 55 31  39 2c 31 2c 69 6e 6b 3b  |720 VDU19,1,ink;|
00003e30  30 3b 0d 20 20 37 33 30  20 49 46 20 6d 6f 64 65  |0;.  730 IF mode|
00003e40  3d 37 20 50 52 4f 43 73  65 76 65 6e 0d 20 20 37  |=7 PROCseven.  7|
00003e50  34 30 20 50 52 4f 43 64  65 6c 61 79 0d 20 20 37  |40 PROCdelay.  7|
00003e60  35 30 20 45 4e 44 50 52  4f 43 0d 20 20 37 36 30  |50 ENDPROC.  760|
00003e70  20 3a 0d 20 20 37 37 30  20 44 45 46 50 52 4f 43  | :.  770 DEFPROC|
00003e80  70 61 70 65 72 0d 20 20  37 38 30 20 70 61 70 65  |paper.  780 pape|
00003e90  72 3d 70 61 70 65 72 2b  31 0d 20 20 37 39 30 20  |r=paper+1.  790 |
00003ea0  49 46 20 70 61 70 65 72  3d 69 6e 6b 20 70 61 70  |IF paper=ink pap|
00003eb0  65 72 3d 70 61 70 65 72  2b 31 0d 20 20 38 30 30  |er=paper+1.  800|
00003ec0  20 49 46 20 70 61 70 65  72 3e 37 20 70 61 70 65  | IF paper>7 pape|
00003ed0  72 3d 31 0d 20 20 38 31  30 20 56 44 55 31 39 2c  |r=1.  810 VDU19,|
00003ee0  30 2c 70 61 70 65 72 3b  30 3b 0d 20 20 38 32 30  |0,paper;0;.  820|
00003ef0  20 49 46 20 6d 6f 64 65  3d 37 20 50 52 4f 43 73  | IF mode=7 PROCs|
00003f00  65 76 65 6e 0d 20 20 38  33 30 20 50 52 4f 43 64  |even.  830 PROCd|
00003f10  65 6c 61 79 0d 20 20 38  34 30 20 45 4e 44 50 52  |elay.  840 ENDPR|
00003f20  4f 43 0d 20 20 38 35 30  20 3a 0d 20 20 38 36 30  |OC.  850 :.  860|
00003f30  20 44 45 46 50 52 4f 43  73 65 76 65 6e 0d 20 20  | DEFPROCseven.  |
00003f40  38 37 30 20 49 46 20 69  6e 6b 3d 30 20 69 6e 6b  |870 IF ink=0 ink|
00003f50  3d 31 0d 20 20 38 38 30  20 46 4f 52 20 6c 69 6e  |=1.  880 FOR lin|
00003f60  65 3d 30 20 54 4f 20 32  34 0d 20 20 38 39 30 20  |e=0 TO 24.  890 |
00003f70  49 46 20 70 61 70 65 72  3d 30 20 56 44 55 33 31  |IF paper=0 VDU31|
00003f80  2c 30 2c 6c 69 6e 65 2c  31 32 38 2b 69 6e 6b 2c  |,0,line,128+ink,|
00003f90  33 32 2c 33 32 0d 20 20  20 20 20 20 45 4c 53 45  |32,32.      ELSE|
00003fa0  20 56 44 55 33 31 2c 30  2c 6c 69 6e 65 2c 31 32  | VDU31,0,line,12|
00003fb0  38 2b 70 61 70 65 72 2c  31 35 37 2c 31 32 38 2b  |8+paper,157,128+|
00003fc0  69 6e 6b 0d 20 20 39 30  30 20 4e 45 58 54 0d 20  |ink.  900 NEXT. |
00003fd0  20 39 31 30 20 50 52 4f  43 64 65 6c 61 79 0d 20  | 910 PROCdelay. |
00003fe0  20 39 32 30 20 45 4e 44  50 52 4f 43 0d 20 20 39  | 920 ENDPROC.  9|
00003ff0  33 30 20 3a 0d 20 20 39  34 30 20 44 45 46 50 52  |30 :.  940 DEFPR|
00004000  4f 43 6d 63 6f 64 65 0d  20 20 39 35 30 20 66 69  |OCmcode.  950 fi|
00004010  72 65 3d 26 37 32 20 3a  52 45 4d 3a 20 66 69 72  |re=&72 :REM: fir|
00004020  65 20 62 75 74 74 6f 6e  20 73 74 61 74 75 73 0d  |e button status.|
00004030  20 20 39 36 30 20 69 72  71 32 76 3d 26 32 30 36  |  960 irq2v=&206|
00004040  20 3a 52 45 4d 3a 20 73  65 63 6f 6e 64 61 72 79  | :REM: secondary|
00004050  20 69 6e 74 65 72 72 75  70 74 20 76 65 63 74 6f  | interrupt vecto|
00004060  72 0d 20 20 39 37 30 20  73 63 72 65 65 6e 3d 26  |r.  970 screen=&|
00004070  33 35 35 20 3a 52 45 4d  3a 20 73 63 72 65 65 6e  |355 :REM: screen|
00004080  20 6d 6f 64 65 20 4f 53  20 31 2e 32 0d 20 20 39  | mode OS 1.2.  9|
00004090  38 30 20 73 68 65 69 6c  61 3d 26 46 45 30 30 0d  |80 sheila=&FE00.|
000040a0  20 20 39 39 30 20 64 72  62 3d 26 46 45 34 30 20  |  990 drb=&FE40 |
000040b0  3a 52 45 4d 3a 20 73 79  73 74 65 6d 20 36 35 32  |:REM: system 652|
000040c0  32 20 69 6e 70 75 74 2f  6f 75 74 70 75 74 20 72  |2 input/output r|
000040d0  65 67 69 73 74 65 72 20  42 0d 20 31 30 30 30 20  |egister B. 1000 |
000040e0  69 66 72 3d 26 46 45 34  44 20 3a 52 45 4d 3a 20  |ifr=&FE4D :REM: |
000040f0  73 79 73 74 65 6d 20 36  35 32 32 20 69 6e 74 65  |system 6522 inte|
00004100  72 72 75 70 74 20 66 6c  61 67 20 72 65 67 69 73  |rrupt flag regis|
00004110  74 65 72 0d 20 31 30 31  30 20 69 65 72 3d 26 46  |ter. 1010 ier=&F|
00004120  45 34 45 20 3a 52 45 4d  3a 20 73 79 73 74 65 6d  |E4E :REM: system|
00004130  20 36 35 32 32 20 69 6e  74 65 72 72 75 70 74 20  | 6522 interrupt |
00004140  65 6e 61 62 6c 65 20 72  65 67 69 73 74 65 72 0d  |enable register.|
00004150  20 31 30 32 30 20 6f 73  77 6f 72 64 3d 26 46 46  | 1020 osword=&FF|
00004160  46 31 0d 20 31 30 33 30  20 6f 73 62 79 74 65 3d  |F1. 1030 osbyte=|
00004170  26 46 46 46 34 0d 20 31  30 34 30 20 46 4f 52 20  |&FFF4. 1040 FOR |
00004180  70 61 73 73 3d 30 20 54  4f 20 32 20 53 54 45 50  |pass=0 TO 2 STEP|
00004190  20 32 0d 20 31 30 35 30  20 50 25 3d 6d 63 6f 64  | 2. 1050 P%=mcod|
000041a0  65 0d 20 31 30 36 30 20  5b 20 20 20 20 20 20 20  |e. 1060 [       |
000041b0  4f 50 54 20 70 61 73 73  0d 20 31 30 37 30 20 20  |OPT pass. 1070  |
000041c0  20 20 20 20 20 20 20 4c  44 58 20 69 72 71 32 76  |       LDX irq2v|
000041d0  20 20 20 20 20 5c 20 73  65 63 6f 6e 64 61 72 79  |     \ secondary|
000041e0  20 69 6e 74 65 72 72 75  70 74 20 76 65 63 74 6f  | interrupt vecto|
000041f0  72 2c 20 6c 6f 77 20 62  79 74 65 0d 20 31 30 38  |r, low byte. 108|
00004200  30 20 20 20 20 20 20 20  20 20 4c 44 59 20 69 72  |0         LDY ir|
00004210  71 32 76 2b 31 20 20 20  5c 20 73 65 63 6f 6e 64  |q2v+1   \ second|
00004220  61 72 79 20 69 6e 74 65  72 72 75 70 74 20 76 65  |ary interrupt ve|
00004230  63 74 6f 72 2c 20 68 69  67 68 20 62 79 74 65 0d  |ctor, high byte.|
00004240  20 31 30 39 30 20 20 20  20 20 20 20 20 20 43 50  | 1090         CP|
00004250  59 20 23 69 6e 74 65 72  72 75 70 74 20 44 49 56  |Y #interrupt DIV|
00004260  20 32 35 36 20 5c 20 68  61 73 20 74 68 65 20 68  | 256 \ has the h|
00004270  69 67 68 20 62 79 74 65  20 62 65 65 6e 20 61 6c  |igh byte been al|
00004280  74 65 72 65 64 3f 0d 20  31 31 30 30 20 20 20 20  |tered?. 1100    |
00004290  20 20 20 20 20 42 45 51  20 64 69 73 61 62 6c 65  |     BEQ disable|
000042a0  20 20 20 5c 20 72 65 73  74 6f 72 65 20 6f 72 69  |   \ restore ori|
000042b0  67 69 6e 61 6c 20 76 65  63 74 6f 72 20 69 66 20  |ginal vector if |
000042c0  61 6c 74 65 72 65 64 0d  20 31 31 31 30 20 20 20  |altered. 1110   |
000042d0  20 20 20 20 20 20 53 54  58 20 6f 6c 64 69 72 71  |      STX oldirq|
000042e0  32 76 20 20 5c 20 73 74  6f 72 65 20 6f 72 69 67  |2v  \ store orig|
000042f0  69 6e 61 6c 20 76 65 63  74 6f 72 2c 20 6c 6f 77  |inal vector, low|
00004300  20 62 79 74 65 0d 20 31  31 32 30 20 20 20 20 20  | byte. 1120     |
00004310  20 20 20 20 53 54 59 20  6f 6c 64 69 72 71 32 76  |    STY oldirq2v|
00004320  2b 31 20 5c 20 73 74 6f  72 65 20 6f 72 69 67 69  |+1 \ store origi|
00004330  6e 61 6c 20 76 65 63 74  6f 72 2c 20 68 69 67 68  |nal vector, high|
00004340  20 62 79 74 65 0d 20 31  31 33 30 20 20 20 20 20  | byte. 1130     |
00004350  20 20 20 20 4c 44 58 20  23 69 6e 74 65 72 72 75  |    LDX #interru|
00004360  70 74 20 4d 4f 44 20 32  35 36 20 5c 20 6e 65 77  |pt MOD 256 \ new|
00004370  20 69 6e 74 65 72 72 75  70 74 20 63 6f 64 65 2c  | interrupt code,|
00004380  20 6c 6f 77 20 62 79 74  65 0d 20 31 31 34 30 20  | low byte. 1140 |
00004390  20 20 20 20 20 20 20 20  4c 44 59 20 23 69 6e 74  |        LDY #int|
000043a0  65 72 72 75 70 74 20 44  49 56 20 32 35 36 20 5c  |errupt DIV 256 \|
000043b0  20 6e 65 77 20 69 6e 74  65 72 72 75 70 74 20 63  | new interrupt c|
000043c0  6f 64 65 2c 20 68 69 67  68 20 62 79 74 65 0d 20  |ode, high byte. |
000043d0  31 31 35 30 20 20 20 20  20 20 20 20 20 53 45 49  |1150         SEI|
000043e0  20 20 20 20 20 20 20 20  20 20 20 5c 20 73 65 74  |           \ set|
000043f0  20 69 6e 74 65 72 72 75  70 74 20 64 69 73 61 62  | interrupt disab|
00004400  6c 65 20 66 6c 61 67 0d  20 31 31 36 30 20 20 20  |le flag. 1160   |
00004410  20 20 20 20 20 20 53 54  58 20 69 72 71 32 76 20  |      STX irq2v |
00004420  20 20 20 20 5c 20 61 6c  74 65 72 20 76 65 63 74  |    \ alter vect|
00004430  6f 72 2c 20 6c 6f 77 20  62 79 74 65 0d 20 31 31  |or, low byte. 11|
00004440  37 30 20 20 20 20 20 20  20 20 20 53 54 59 20 69  |70         STY i|
00004450  72 71 32 76 2b 31 20 20  20 5c 20 61 6c 74 65 72  |rq2v+1   \ alter|
00004460  20 76 65 63 74 6f 72 2c  20 68 69 67 68 20 62 79  | vector, high by|
00004470  74 65 0d 20 31 31 38 30  20 20 20 20 20 20 20 20  |te. 1180        |
00004480  20 43 4c 49 20 20 20 20  20 20 20 20 20 20 20 5c  | CLI           \|
00004490  20 63 6c 65 61 72 20 69  6e 74 65 72 72 75 70 74  | clear interrupt|
000044a0  20 64 69 73 61 62 6c 65  20 66 6c 61 67 0d 20 31  | disable flag. 1|
000044b0  31 39 30 20 20 20 20 20  20 20 20 20 4c 44 41 20  |190         LDA |
000044c0  23 26 38 38 20 20 20 20  20 20 5c 20 25 31 30 30  |#&88      \ %100|
000044d0  30 31 30 30 30 0d 20 31  32 30 30 20 20 20 20 20  |01000. 1200     |
000044e0  20 20 20 20 53 54 41 20  69 65 72 20 20 20 20 20  |    STA ier     |
000044f0  20 20 5c 20 65 6e 61 62  6c 65 20 6c 69 67 68 74  |  \ enable light|
00004500  20 70 65 6e 20 69 6e 74  65 72 72 75 70 74 73 0d  | pen interrupts.|
00004510  20 31 32 31 30 20 5c 20  20 20 20 20 20 20 4c 44  | 1210 \       LD|
00004520  41 20 23 26 45 39 20 20  20 20 20 20 5c 20 77 72  |A #&E9      \ wr|
00004530  69 74 65 20 73 79 73 74  65 6d 20 56 49 41 20 49  |ite system VIA I|
00004540  52 51 20 62 69 74 20 6d  61 73 6b 0d 20 31 32 32  |RQ bit mask. 122|
00004550  30 20 5c 20 20 20 20 20  20 20 4c 44 58 20 23 26  |0 \       LDX #&|
00004560  46 37 20 20 20 20 20 20  5c 20 25 31 31 31 31 30  |F7      \ %11110|
00004570  31 31 31 0d 20 31 32 33  30 20 5c 20 20 20 20 20  |111. 1230 \     |
00004580  20 20 4c 44 59 20 23 26  30 30 0d 20 31 32 34 30  |  LDY #&00. 1240|
00004590  20 5c 20 20 20 20 20 20  20 4a 53 52 20 6f 73 62  | \       JSR osb|
000045a0  79 74 65 20 20 20 20 5c  20 62 69 74 20 6d 61 73  |yte    \ bit mas|
000045b0  6b 20 3d 20 25 31 31 31  31 30 31 31 31 0d 20 31  |k = %11110111. 1|
000045c0  32 35 30 20 20 20 20 20  20 20 20 20 52 54 53 0d  |250         RTS.|
000045d0  20 31 32 36 30 20 2e 64  69 73 61 62 6c 65 0d 20  | 1260 .disable. |
000045e0  31 32 37 30 20 20 20 20  20 20 20 20 20 4c 44 41  |1270         LDA|
000045f0  20 23 26 30 38 20 20 20  20 20 20 5c 20 25 30 30  | #&08      \ %00|
00004600  30 30 31 30 30 30 20 72  65 61 64 79 20 74 6f 20  |001000 ready to |
00004610  64 69 73 61 62 6c 65 20  6c 69 67 68 74 20 70 65  |disable light pe|
00004620  6e 0d 20 20 20 20 20 20  20 20 20 20 20 20 20 20  |n.              |
00004630  20 20 20 20 20 20 20 20  20 20 20 20 20 20 5c 20  |              \ |
00004640  69 6e 74 65 72 72 75 70  74 73 0d 20 31 32 38 30  |interrupts. 1280|
00004650  20 20 20 20 20 20 20 20  20 4c 44 58 20 6f 6c 64  |         LDX old|
00004660  69 72 71 32 76 20 20 5c  20 6f 72 69 67 69 6e 61  |irq2v  \ origina|
00004670  6c 20 69 72 71 32 20 76  65 63 74 6f 72 2c 20 6c  |l irq2 vector, l|
00004680  6f 77 20 62 79 74 65 0d  20 31 32 39 30 20 20 20  |ow byte. 1290   |
00004690  20 20 20 20 20 20 4c 44  59 20 6f 6c 64 69 72 71  |      LDY oldirq|
000046a0  32 76 2b 31 20 5c 20 6f  72 69 67 69 6e 61 6c 20  |2v+1 \ original |
000046b0  69 72 71 32 20 76 65 63  74 6f 72 2c 20 68 69 67  |irq2 vector, hig|
000046c0  68 20 62 79 74 65 0d 20  31 33 30 30 20 20 20 20  |h byte. 1300    |
000046d0  20 20 20 20 20 53 45 49  20 20 20 20 20 20 20 20  |     SEI        |
000046e0  20 20 20 5c 20 73 65 74  20 69 6e 74 65 72 72 75  |   \ set interru|
000046f0  70 74 20 64 69 73 61 62  6c 65 20 66 6c 61 67 0d  |pt disable flag.|
00004700  20 31 33 31 30 20 20 20  20 20 20 20 20 20 53 54  | 1310         ST|
00004710  41 20 69 65 72 20 20 20  20 20 20 20 5c 20 64 69  |A ier       \ di|
00004720  73 61 62 6c 65 20 6c 69  67 68 74 20 70 65 6e 20  |sable light pen |
00004730  69 6e 74 65 72 72 75 70  74 0d 20 31 33 32 30 20  |interrupt. 1320 |
00004740  20 20 20 20 20 20 20 20  53 54 58 20 69 72 71 32  |        STX irq2|
00004750  76 20 20 20 20 20 5c 20  72 65 73 74 6f 72 65 20  |v     \ restore |
00004760  6f 72 69 67 69 6e 61 6c  20 76 65 63 74 6f 72 2c  |original vector,|
00004770  20 6c 6f 77 20 62 79 74  65 0d 20 31 33 33 30 20  | low byte. 1330 |
00004780  20 20 20 20 20 20 20 20  53 54 59 20 69 72 71 32  |        STY irq2|
00004790  76 2b 31 20 20 20 5c 20  72 65 73 74 6f 72 65 20  |v+1   \ restore |
000047a0  6f 72 69 67 69 6e 61 6c  20 76 65 63 74 6f 72 2c  |original vector,|
000047b0  20 68 69 67 68 20 62 79  74 65 0d 20 31 33 34 30  | high byte. 1340|
000047c0  20 20 20 20 20 20 20 20  20 43 4c 49 20 20 20 20  |         CLI    |
000047d0  20 20 20 20 20 20 20 5c  20 63 6c 65 61 72 20 69  |       \ clear i|
000047e0  6e 74 65 72 72 75 70 74  20 64 69 73 61 62 6c 65  |nterrupt disable|
000047f0  20 66 6c 61 67 0d 20 31  33 35 30 20 5c 20 20 20  | flag. 1350 \   |
00004800  20 20 20 20 4c 44 41 20  23 26 45 39 20 20 20 20  |    LDA #&E9    |
00004810  20 20 5c 20 77 72 69 74  65 20 73 79 73 74 65 6d  |  \ write system|
00004820  20 56 49 41 20 49 52 51  20 62 69 74 20 6d 61 73  | VIA IRQ bit mas|
00004830  6b 0d 20 31 33 36 30 20  5c 20 20 20 20 20 20 20  |k. 1360 \       |
00004840  4c 44 58 20 23 26 46 46  20 20 20 20 20 20 5c 20  |LDX #&FF      \ |
00004850  25 31 31 31 31 31 31 31  31 0d 20 31 33 37 30 20  |%11111111. 1370 |
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000048b0  52 54 53 0d 20 31 34 30  30 20 2e 65 78 69 74 0d  |RTS. 1400 .exit.|
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000048d0  41 20 20 20 20 20 20 20  20 20 20 20 5c 20 70 75  |A           \ pu|
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00004910  20 20 20 20 20 53 54 41  20 26 46 43 20 20 20 20  |     STA &FC    |
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00004970  65 78 69 74 20 76 69 61  20 6f 72 69 67 69 6e 61  |exit via origina|
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00004990  69 6e 74 65 72 72 75 70  74 0d 20 31 34 35 30 20  |interrupt. 1450 |
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00004ff0  61 72 65 20 66 6f 72 20  73 75 62 74 72 61 63 74  |are for subtract|
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00005040  20 42 43 43 20 64 6f 6e  65 20 20 20 20 20 20 5c  | BCC done      \|
00005050  20 62 72 61 6e 63 68 20  69 66 20 64 69 76 69 64  | branch if divid|
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00005090  65 6d 65 6e 74 20 71 75  6f 74 69 65 6e 74 0d 20  |ement quotient. |
000050a0  31 38 31 30 20 20 20 20  20 20 20 20 20 53 54 41  |1810         STA|
000050b0  20 78 63 6f 6f 72 64 20  20 20 20 5c 20 73 61 76  | xcoord    \ sav|
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000050e0  6e 65 0d 20 31 38 33 30  20 20 20 20 20 20 20 20  |ne. 1830        |
000050f0  20 44 45 58 20 20 20 20  20 20 20 20 20 20 20 5c  | DEX           \|
00005100  20 64 65 63 72 65 6d 65  6e 74 20 62 69 74 20 63  | decrement bit c|
00005110  6f 75 6e 74 65 72 0d 20  31 38 34 30 20 20 20 20  |ounter. 1840    |
00005120  20 20 20 20 20 42 4e 45  20 6e 65 78 74 20 20 20  |     BNE next   |
00005130  20 20 20 5c 20 62 72 61  6e 63 68 20 66 6f 72 20  |   \ branch for |
00005140  31 36 20 62 69 74 73 0d  20 31 38 35 30 20 20 20  |16 bits. 1850   |
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00005160  59 20 20 20 5c 20 73 63  72 65 65 6e 20 6d 6f 64  |Y   \ screen mod|
00005170  65 20 73 63 61 6c 65 0d  20 31 38 36 30 20 20 20  |e scale. 1860   |
00005180  20 20 20 20 20 20 42 45  51 20 70 75 6c 6c 6f 75  |      BEQ pullou|
00005190  74 20 20 20 5c 20 62 72  61 6e 63 68 20 69 66 20  |t   \ branch if |
000051a0  6d 6f 64 65 73 20 30 2c  20 33 2c 20 34 2c 20 36  |modes 0, 3, 4, 6|
000051b0  20 6f 72 20 37 0d 20 31  38 37 30 20 20 20 20 20  | or 7. 1870     |
000051c0  20 20 20 20 54 41 58 20  20 20 20 20 20 20 20 20  |    TAX         |
000051d0  20 20 5c 20 69 6e 20 6d  6f 64 65 31 20 61 6e 64  |  \ in mode1 and|
000051e0  20 6d 6f 64 65 35 20 58  3d 31 2c 20 69 6e 20 6d  | mode5 X=1, in m|
000051f0  6f 64 65 32 20 58 3d 32  0d 20 31 38 38 30 20 20  |ode2 X=2. 1880  |
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00005210  64 0d 20 31 38 39 30 20  2e 72 65 64 75 63 65 0d  |d. 1890 .reduce.|
00005220  20 31 39 30 30 20 20 20  20 20 20 20 20 20 4c 53  | 1900         LS|
00005230  52 20 41 20 20 20 20 20  20 20 20 20 5c 20 68 6f  |R A         \ ho|
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00005250  6e 20 2f 20 32 0d 20 31  39 31 30 20 20 20 20 20  |n / 2. 1910     |
00005260  20 20 20 20 44 45 58 0d  20 31 39 32 30 20 20 20  |    DEX. 1920   |
00005270  20 20 20 20 20 20 42 4e  45 20 72 65 64 75 63 65  |      BNE reduce|
00005280  0d 20 31 39 33 30 20 20  20 20 20 20 20 20 20 53  |. 1930         S|
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000052a0  2e 70 75 6c 6c 6f 75 74  0d 20 31 39 35 30 20 20  |.pullout. 1950  |
000052b0  20 20 20 20 20 20 20 50  4c 41 20 20 20 20 20 20  |       PLA      |
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000052d0  20 72 65 67 69 73 74 65  72 20 42 0d 20 31 39 36  | register B. 196|
000052e0  30 20 20 20 20 20 20 20  20 20 41 4e 44 20 23 26  |0         AND #&|
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00005300  30 30 30 0d 20 31 39 37  30 20 20 20 20 20 20 20  |000. 1970       |
00005310  20 20 53 54 41 20 66 69  72 65 20 20 20 20 20 20  |  STA fire      |
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00005340  20 20 20 20 20 20 20 20  20 50 4c 41 0d 20 31 39  |         PLA. 19|
00005350  39 30 20 20 20 20 20 20  20 20 20 54 41 59 0d 20  |90         TAY. |
00005360  32 30 30 30 20 20 20 20  20 20 20 20 20 50 4c 41  |2000         PLA|
00005370  0d 20 32 30 31 30 20 20  20 20 20 20 20 20 20 54  |. 2010         T|
00005380  41 58 0d 20 32 30 32 30  20 20 20 20 20 20 20 20  |AX. 2020        |
00005390  20 50 4c 41 0d 20 32 30  33 30 20 20 20 20 20 20  | PLA. 2030      |
000053a0  20 20 20 53 54 41 20 26  46 43 0d 20 32 30 34 30  |   STA &FC. 2040|
000053b0  20 20 20 20 20 20 20 20  20 52 54 49 20 20 20 20  |         RTI    |
000053c0  20 20 20 20 20 20 20 5c  20 72 65 74 75 72 6e 20  |       \ return |
000053d0  66 72 6f 6d 20 69 6e 74  65 72 72 75 70 74 0d 20  |from interrupt. |
000053e0  32 30 35 30 20 2e 6f 6c  64 69 72 71 32 76 0d 20  |2050 .oldirq2v. |
000053f0  32 30 36 30 20 20 20 20  20 20 20 20 20 45 51 55  |2060         EQU|
00005400  57 20 26 30 30 20 20 20  20 20 20 5c 20 6f 72 69  |W &00      \ ori|
00005410  67 69 6e 61 6c 20 69 72  71 32 20 76 65 63 74 6f  |ginal irq2 vecto|
00005420  72 0d 20 32 30 37 30 20  2e 6f 66 66 73 65 74 6c  |r. 2070 .offsetl|
00005430  6f 77 0d 20 32 30 38 30  20 20 20 20 20 20 20 20  |ow. 2080        |
00005440  20 45 51 55 42 20 26 30  34 20 20 20 20 20 20 5c  | EQUB &04      \|
00005450  20 6d 6f 64 65 30 2c 20  75 6e 74 72 69 6d 6d 65  | mode0, untrimme|
00005460  64 20 3d 20 26 30 36 0d  20 32 30 39 30 20 20 20  |d = &06. 2090   |
00005470  20 20 20 20 20 20 45 51  55 42 20 26 30 34 20 20  |      EQUB &04  |
00005480  20 20 20 20 5c 20 6d 6f  64 65 31 2c 20 75 6e 74  |    \ mode1, unt|
00005490  72 69 6d 6d 65 64 20 3d  20 26 30 36 0d 20 32 31  |rimmed = &06. 21|
000054a0  30 30 20 20 20 20 20 20  20 20 20 45 51 55 42 20  |00         EQUB |
000054b0  26 30 34 20 20 20 20 20  20 5c 20 6d 6f 64 65 32  |&04      \ mode2|
000054c0  2c 20 75 6e 74 72 69 6d  6d 65 64 20 3d 20 26 30  |, untrimmed = &0|
000054d0  36 0d 20 32 31 31 30 20  20 20 20 20 20 20 20 20  |6. 2110         |
000054e0  45 51 55 42 20 26 30 34  20 20 20 20 20 20 5c 20  |EQUB &04      \ |
000054f0  6d 6f 64 65 33 2c 20 75  6e 74 72 69 6d 6d 65 64  |mode3, untrimmed|
00005500  20 3d 20 26 30 36 0d 20  32 31 32 30 20 20 20 20  | = &06. 2120    |
00005510  20 20 20 20 20 45 51 55  42 20 26 30 33 20 20 20  |     EQUB &03   |
00005520  20 20 20 5c 20 6d 6f 64  65 34 2c 20 75 6e 74 72  |   \ mode4, untr|
00005530  69 6d 6d 65 64 20 3d 20  26 30 34 0d 20 32 31 33  |immed = &04. 213|
00005540  30 20 20 20 20 20 20 20  20 20 45 51 55 42 20 26  |0         EQUB &|
00005550  30 33 20 20 20 20 20 20  5c 20 6d 6f 64 65 35 2c  |03      \ mode5,|
00005560  20 75 6e 74 72 69 6d 6d  65 64 20 3d 20 26 30 34  | untrimmed = &04|
00005570  0d 20 32 31 34 30 20 20  20 20 20 20 20 20 20 45  |. 2140         E|
00005580  51 55 42 20 26 30 33 20  20 20 20 20 20 5c 20 6d  |QUB &03      \ m|
00005590  6f 64 65 36 2c 20 75 6e  74 72 69 6d 6d 65 64 20  |ode6, untrimmed |
000055a0  3d 20 26 30 34 0d 20 32  31 35 30 20 20 20 20 20  |= &04. 2150     |
000055b0  20 20 20 20 45 51 55 42  20 26 30 36 20 20 20 20  |    EQUB &06    |
000055c0  20 20 5c 20 6d 6f 64 65  37 2c 20 75 6e 74 72 69  |  \ mode7, untri|
000055d0  6d 6d 65 64 20 3d 20 26  30 38 0d 20 32 31 36 30  |mmed = &08. 2160|
000055e0  20 2e 6f 66 66 73 65 74  68 69 67 68 0d 20 32 31  | .offsethigh. 21|
000055f0  37 30 20 20 20 20 20 20  20 20 20 45 51 55 44 20  |70         EQUD |
00005600  26 30 38 30 36 30 36 30  36 20 5c 20 6d 6f 64 65  |&08060606 \ mode|
00005610  73 20 33 2d 30 0d 20 32  31 38 30 20 20 20 20 20  |s 3-0. 2180     |
00005620  20 20 20 20 45 51 55 44  20 26 32 38 30 43 30 42  |    EQUD &280C0B|
00005630  30 42 20 5c 20 6d 6f 64  65 73 20 37 2d 34 0d 20  |0B \ modes 7-4. |
00005640  32 31 39 30 20 2e 73 63  61 6c 65 0d 20 32 32 30  |2190 .scale. 220|
00005650  30 20 20 20 20 20 20 20  20 20 45 51 55 44 20 26  |0         EQUD &|
00005660  30 30 30 32 30 31 30 30  20 5c 20 6d 6f 64 65 73  |00020100 \ modes|
00005670  20 33 2d 30 0d 20 32 32  31 30 20 20 20 20 20 20  | 3-0. 2210      |
00005680  20 20 20 45 51 55 44 20  26 30 30 30 30 30 31 30  |   EQUD &0000010|
00005690  30 20 5c 20 6d 6f 64 65  73 20 37 2d 34 0d 20 32  |0 \ modes 7-4. 2|
000056a0  32 32 30 20 2e 77 69 64  74 68 0d 20 32 32 33 30  |220 .width. 2230|
000056b0  20 20 20 20 20 20 20 20  20 45 51 55 44 20 26 35  |         EQUD &5|
000056c0  30 35 30 35 30 35 30 20  5c 20 6d 6f 64 65 73 20  |0505050 \ modes |
000056d0  33 2d 30 0d 20 32 32 34  30 20 20 20 20 20 20 20  |3-0. 2240       |
000056e0  20 20 45 51 55 44 20 26  32 38 32 38 32 38 32 38  |  EQUD &28282828|
000056f0  20 5c 20 6d 6f 64 65 73  20 37 2d 34 0d 20 32 32  | \ modes 7-4. 22|
00005700  35 30 20 2e 6c 61 73 74  62 79 74 65 0d 20 32 32  |50 .lastbyte. 22|
00005710  36 30 20 5d 0d 20 32 32  37 30 20 4e 45 58 54 0d  |60 ]. 2270 NEXT.|
00005720  20 32 32 38 30 20 43 41  4c 4c 20 6d 63 6f 64 65  | 2280 CALL mcode|
00005730  0d 20 32 32 39 30 20 45  4e 44 50 52 4f 43 0d 20  |. 2290 ENDPROC. |
00005740  32 33 30 30 20 3a 20 0d  20 32 33 31 30 20 44 45  |2300 : . 2310 DE|
00005750  46 46 4e 73 77 69 74 63  68 0d 20 32 33 32 30 20  |FFNswitch. 2320 |
00005760  49 46 20 28 41 44 56 41  4c 28 30 29 41 4e 44 33  |IF (ADVAL(0)AND3|
00005770  29 3d 30 20 3d 54 52 55  45 20 45 4c 53 45 20 3d  |)=0 =TRUE ELSE =|
00005780  46 41 4c 53 45 0d                                 |FALSE.|
00005786